In placental mammals, pregnancy usually is associated with an increase in maternal androgens, which may significantly impact fetal growth and differentiation, and affect postnatal development and behavior. Owing to their slow life histories and challenging social conditions, determination of maternal androgens and potential interference effects of fetal androgen production are of particular interest in wild primates. However, androgen production has been rarely investigated in wild female primates, and studies on maternal androgens during gestation in particular often do not span the entire pregnancy. Here, we characterize fecal androgen production throughout gestation in wild Assamese macaques (Macaca assamensis) using noninvasive hormone analysis and, furthermore, examine fetal sex effects on maternal androgen excretion. A total of 207 fecal samples were analyzed from seven females for concentrations of immunoreactive epiandrosterone (iEA). Fecal iEA concentrations, as predicted based on cercopithecine blood-serum patterns, increased during early gestation and were significantly higher during the first trimester compared with preconception concentrations and those recorded during later stages of gestation. Further, during the third trimester, male-carrying mothers showed significantly higher iEA concentrations compared with female-carrying mothers. This first characterization of fecal androgen excretion during gestation in Assamese macaques indicates both a maternal and fetal effect on androgen production. Although our sample size is small, our results, nevertheless, provide the basis for assessing potential influences of maternal androgens on postnatal offspring development and behavior. Am J Phys Anthropol 147:334–339, 2012. © 2011 Wiley Periodicals, Inc.