Second Toughest in the Infants is the fourth album by Underworld, and the second in their "MK2" line-up with Darren Emerson. With this album, Underworld expanded on their progressive palette, while developing their signature sound of abrasive beats and anthemic melodies. The curious name of the album derives from a comment made by member Rick Smith's six-year-old nephew, Simon Prosser, when asked on his progress at infant school (the level of schooling attended by four- to seven-year-old children in the United Kingdom): "Yeah, don't worry about me, I'm second toughest in the infants now".Second Toughest featured the single "Pearl's Girl". The re-issue featured the band's best known single, "Born Slippy .NUXX".
The album was remastered and re-released on 20 November 2015 with deluxe and super-deluxe expanded editions.
The album opens with the multi-song suite "Juanita : Kiteless : To Dream of Love", which features all three parts intersecting each other at various points during the piece; hence, the use of colons instead of slashes in its name. The loungy, drum and bass track "Banstyle" follows, alongside its downtempo, half-speed counterpart "Sappy's Curry". The rest of the record showcases advancements in the Underworld sound: both "Rowla" and "Pearl's Girl" feature club-ready abrasive beats and basslines, while "Blueski" and "Stagger" incorporate live acoustic guitar and light, melancholic arrangements, respectively. "Pearl's Girl" is one of the few Underworld songs to use breakbeats.
Due to the success of the single" Born Slippy .NUXX", Second Toughest was re-issued with a bonus disc containing the single-only tracks "Born Slippy .NUXX" and "Rez"; Japanese editions also featured "Cherry Pie" and the "(Carp Dreams... Koi)" mix of "Pearl's Girl".
The song titles "Sappy's Curry", "Pearl's Girl" and "Born Slippy" all come from the names of greyhounds from an English racing stadium. These greyhounds finished third, second, and first during Underworld's visit to the races.
Like their previous effort dubnobasswithmyheadman, Second Toughest in the Infants received critical acclaim. Stephen Thomas Erlewine of AllMusic wrote that Second Toughest in the Infants "carries the same knockout punch of their debut, Dubnobasswithmyheadman, but it's subtler and more varied, offering proof that the outfit is one of the leading dance collectives of the mid-'90s." Anya Sacharow of Entertainment Weekly stated that Underworld "know how to expand the frenzy of techno and jungle and then retreat to an ambient cool" and that "the art is in the segue", while NME stated that the album has a "smooth of touch, sleek of footing and downright slippery of rhythm, the anti-Green Day trio breezily persevere in their quest for Western groove domination." The album is featured in the book 1001 Albums You Must Hear Before You Die.
In 2015, the album was reissued on vinyl and 2-CD and 4-CD expanded editions. Highlighting alternate mixes, remixes and unreleased songs, the 4-CD version includes a full CD of variations of "Born Slippy .NUXX", from one of the song's earliest versions in 1994, up until its final form a year later (which is included here in its 1996 extended form). Paul Simpson from AllMusic in his retrospective review said that "Second Toughest in the Infants endures as a landmark album, spotlighting Underworld at their creative peak, and remaining an important document of an era when experimental, cerebral electronic dance music received significant mainstream attention."