Analysis of reproductive performance for four species of callitrichids maintained in our laboratory shows conception rates to vary from 3.14 for S. weddelli to 1.01 for S. fuscicollis lagonotus. Delivery rates vary from 0.55 for S. fuscicollis nigrifrons to 0.90 for S. weddelli. There is no seasonal pattern of births for any of the species maintained in the laboratory. Abdominal palpation of females has proven useful for predicting the date of parturition and assessing development of the fetus. Abortions occur among all species and tend to occur during the first third of gestation in C. jacchus and the last third of gestation in S. oedipus.