This article describes a Berlin ‘Tierpark’ group of orang utans. 10 pregnancies occurred in this group between 1965 and 1973; 9 youngs were born, of which 8 are still living. 1 month after conception, certain changes in the vulva’s appearance are already noticeable, indicating the onset of pregnancy. It was possible to make a detailed study of some of the confinements. The results are recorded here as a basis of comparisons for and to offer suggestions to other primatologists. (Translation by Mrs. Nicole Duplaix-Hall, Editor of International Zoo Yearbook.)