Abstract
The Nonhuman Primate Pregnancy Test (NPPT) kit and the Gravindex Slide Test (GST) were compared for the diagnosis of pregnancy in an orangutan [Pongo pygmaeus]. The NPPT consistently detected chorionic gonadotropin in urine, earlier and longer than the GST. During approximately the last trimester of pregnancy, both tests registered negative results. The NPPT is a simple, effective pregnancy test for breeding age orangutans.