At the Moscow Olympics, Prokofyev was fourth in the 110 m hurdles and won the gold medal running the anchoring leg of the Soviet 4 × 100 m relay team. At the 1982 European Championships, Prokofyev won the silver medal in the 110 m hurdles and again a gold in the 4 × 100 m relay. At the first World Championships, Prokofyev was eliminated in the heats of the 110 m hurdles, but won a bronze medal as a member of the Soviet 4 × 100 m relay team.
|Representing Soviet Union|
|1980||Olympic Games||Moscow, Soviet Union||1st||4 × 100 m relay||38.26 s|
|1982||European Championships||Athens, Greece||1st||4 × 100 m relay||38.60 s|
|2nd||110 m hurdles||13.46 s|
|1983||World Championships||Helsinki, Finland||3rd||4 × 100 m relay||38.41 s|
|1986||Goodwill Games||Moscow, Soviet Union||2nd||110 m hurdles||13.28 s|