During his trances, Ramakrishna seemed to become unconscious and sat in a fixed position for a short time, or for hours, and would then slowly return to normal consciousness. When he was in this condition, doctors could find no trace of pulse or heart beat. It is also said that he already had the power of inducing samādhi in others. Some claimed that these recurrent trances left his body extraordinarily sensitive and delicate.
According to his biographers, Ramakrishna's trances were accompanied by low metabolic rate, reduction of respiration and heart-rate, high-body temperature, tremor of the fingers. It is also mentioned that after divine visions during this spiritual sadhana, usually the next day, Ramakrishna used to feel intense pain, so he eventually used to resist the vision to avoid the pain.
Ramakrishna described his trances as a "limitless infinite, effulgent ocean of consciousness or spirit".
Mahendralal Sarkar, a physician of Calcutta who treated Ramakrishna during his final days is one of the firsthand witnesses who examined Ramakrishna during his samadhi. Sarkar reportedly was a rationalist, who did not share the religious views of Ramakrishna, nor did he see him as an avatar He was present during several ecstasies of Ramakrishna and studied them from a medical point of view. He claimed that the stethoscopic examination of the heart and the condition of the eyes during samadhi showed all the symptoms of death, and, when Ramakrishna's actually died, he could not distinguish his death from normal samadhi.
Somnath Bhattacharyya, a psychoanalyst and psychologist, claimed that Ramakrishna's samadhi states were accompanied by very profound inward withdrawal of consciousness, and remarkable physiological changes, consistent with the highest stages of meditative absorption as documented in Hindu Tantra, Yoga and Buddhist literature.
G. C. Ray of IIT analyzed Ramakrishna's EEGs and ECG during his trances. He suggests that, during the trance, some physiological subsystems of the body may be switched off. The author also suggests that, "this process of gradually dropping the subsystems may be same as "neti, neti" (not this, not this, ... and reject it in the journey towards ultimate reality) as is voiced in the Upanishads".
Bhagavan Rudra was another who treated the Ramakrishna. During one of his visits, Ramakrishna asked a devotee to bring a rupee coin. When he held it in his hand, the hand began to writhe and he reported feeling pain. His breathing also stopped. After the coin had been taken away, he breathed deeply three times and relaxed his hand. Rudra ascribed this behavior to "action on the nerves." Ramakrishna also told Rudra that when a knot was tied in the corner of his cloth, he could not breathe until the knot was untied.
It is reported that in 1881, when Ramakrishna was once in ecstasy, another medical doctor touched the eyeballs of Ramakrishna to test if his ecstasy was a real one. He was surprised to find no reaction from Ramakrishna.
Swami Vivekananda, who would later become Ramakrishna's most ardent and prominent disciple, initially viewed Ramakrishna's ecstasy as pathological, and his visions as "creations of a sick brain, mere hallucinations".
- St. Paul, after a similar experience, was struck blind.
- Suso, a German mystic of the 14th century, suffered at the time of his awakening so greatly in body that it seemed to him that none even in dying could suffer so much in so short a time.
- Richard Rolle of Hampole has recorded that his heart burned with a sensible fire, "truly not imaginingly." 
- St.Theresa of Avila.
Walter G. Neevel and Bardwell L. Smith  argue that Ramakrishna's ability to easily enter into trances was largely due to "his esthetic and emotional sensitivity — his capacity to so appreciate and identify with beauty and harmony in what he saw and did".
Leo Schneiderman claimed that Ramakrishna's samādhi, like his other "bizarre" behavior could be understood in the context of the broad tradition of Hinduism, village shamanism, and the non-Sanskritic popular culture.
- Isherwood, Christopher (1964). "The Vision of Kali". Ramakrishna and his Disciples. pp. 63–64.
- Farquhar, J. N. (2003). Modern Religious Movements in India. Kessinger Publishing. p. 189.
- Banhatti, G.S. "Spiritual Apprenticeship". Life and Philosophy of Swami Vivekananda. Atlantic Publishers & Distributors. p. 9. ISBN 978-81-7156-291-6.
- Isherwood, Christopher (1945). Vedanta for the Western World: A Symposium on Vedanta. Vedanta Press. p. 20.
- Ray, G.C. (2002-08-06). "Journey through higher consciousness and the physiological changes". IEEE: 59–60. doi:10.1109/RCEMBS.1995.508689. Retrieved 2008-10-04.
- Rolland, Romain (1929). "Ramakrishna and the Great Shepherds of India". The Life of Ramakrishna. pp. 110–130.
- Rolland, Romain (1929). "The River Re-Enters the Sea". The Life of Ramakrishna. pp. 204–205. "To say that the Infinite came down to earth in the form of a man is the ruin of all religions."
- Bhattacharyya, Professor Somnath. "Kali's Child: Psychological And Hermeneutical Problems". Infinity Foundation. Retrieved 2008-08-23.
- Atmakama (October 2008). "The Doctors Who Met Sri Ramakrishna". The Vedanta Kesari 95 (10): 393–397. ISSN 0042-2983.
- Clarke, Peter Bernard (2006). New Religions in Global Perspective. Routledge. p. 209. "[Vivekananda was] at one time a member of the protestant-like, puritanical, anti-image worshipping, and deistic Brahmo Samaj movement."
- Rolland, Romain (1929). "Naren the Beloved Disciple". The Life of Ramakrishna. pp. 169–193.
- Rolland, Romain (1929). "Kali the Mother". The Life of Ramakrishna. p. 16.
- Jeffrey Moussaieff Masson (1980). "The oceanic feeling : Origin of the term". The oceanic feeling: The Origins of Religious Sentiment in Ancient India. Springer. p. 33.
- D. S. Sarma (1927), The Experience of Sri Ramakrishna Paramahamsa. The Journal of Religion, volume 7 issue 2, pages 186–203. The University of Chicago Press. Online version at jstor.org.
- Walter G. Neevel and Bardwell L. Smith (1976), Hinduism: New Essays in the History of Religions, chapter The Transformation of Ramakrishna, pages 53–97. Brill Archive.
- Leo Schneiderman (1969), Ramakrishna: Personality and Social Factors in the Growth of a Religious Movement. Journal for the Scientific Study of Religion, volume 8, pages 60–71. Online version at Jstor.org.