By retrospective review of colony records and determinations of urinary hormones we have described the reproductive profile of the female pygmy marmoset (Cebuella pygmaea). The pygmy marmoset is a nonseasonal breeder and gives birth to twins 76% of the time with single births occurring 16% and triplet births 8% of the time. lnterbirth intervals ranged from 149-746 days. First births occurred to females between 24-42 months of age and 5-27 months post pairing. We measured urinary estrone, estradiol and estrone conjugates along with immunoreactive luteinizing hormone/chorionic gonadotropin (LH/CG). The postpartum LH peak occurred a mean of 15.6 days following parturition. The conception rate was 69% following the postpartum ovulation. Levels of CG rose a mean of 19 days following the LH peak in conceptive cycles and remained elevated for a mean of 76 days. Gestational length was a mean of 141.9 days from the LH peak to parturition. Only one female of the five studied displayed ovarian cycles which were a mean of 27 days in length. Estradiol was the predominant urinary estrogen, however both estrone and estradiol were excreted in extremely high concentrations. LH peaks were discrete with urinary estrogens increasing at the time of the LH peak and remaining elevated throughout the luteal phase of the cycle.