Abstract: Since November,1989 a study about the reproduction of Middle slow Loris (Nycticebus intermedius) in captivity has been made.All the adults were wildly born.During the summer and fall they were housed in a cage.The size of the cage was 10 square meters and the height of it was 3.5 meters.During the winter and spring they were housed in a room.So far 14 infants were born.The paper presents the main results of the study.Nycticebus intermedius was a highly seasonal breeder.Estrous cycle was from July to September every year.The duration of the cycle was about 49.67 days (SD=1.25).During the estrous cycle,the vaginae of females became swelling and reddening;the testes of males became bigger and the scrotal sacs acquired reticulated pigmentation,glans penises became purple red.During non-breeding season glans penises were pink.Seven copulatory bouts were observed,they occurred during 20:10-22:50,and lasted from 30 seconds to 2 minutes 57 seconds.In six of them,the females suspended themselves upside down with their two hands and two feet beneath the top of cage,the males mounted the females dorsoventrally.Only one copulatory bout was that a female suspended itself with two hands and a foot,a male mounted it ventra-ventrally.Gestation length was about 188 days.All parturition occurred in sprin.Litter size was two.The body weight of newborn babies were about 17.57 g (SD=2.06).Lactation length was about 108 days (SD=4.12).