Specimens from three species of the Callicebus moloch group--C. moloch (N = 80), C. brunneus (N = 166), and C. cupreus (N = 23)--were studied. Twenty genetic loci were investigated through electrophoresis, genetic distances were estimated, and the results compared with the available cytogenetic data. Low values of genetic distance were encountered, contrasting with relatively large chromosome differences. We propose that recent karyotypic rearrangements, rather than other Pleistocene events, were the major evolutionary mechanisms determining speciation in these three taxa.