This article examines the question of whether the congenital red/green color vision defects that are common in human populations can be detected in other catarrhine primates. Spectral sensitivity functions obtained from more than 100 Old World monkeys and apes reveal no hint of such individual variation. A literature survey on the subject leads to the same conclusion and provides the further inference that, if color defects do exist in these nonhuman primates, they must be rare. Two classes of explanation for the apparent low incidence of color defects in Old World monkeys and apes are discussed. (C) 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S123-S127, 2001.