A statistical survey was performed in 1982 to ascertain the incidence of various diseases, especially trauma, in the cynomolgus monkey colony at Tsukuba Primate Center for Medical Science. In total, 1,029 cases of disease, occurred of which 866, 89 and 74 were surgical, internals and reproductive disease cases, respectively (Table 1). Among the 866 surgical cases, trauma (746 cases) was most often observed (Table 2). It was shown that trauma occurred most frequently during the group feeding of juvenile monkeys (Table 3). Analysis of the factors influencing the incidence of trauma during group feeding was carried out. As a result, it was revealed that the number of days after beginning group feeding and the age at which group feeding was begun had marked influences on the incidence of trauma (Figs. 1 and 2). However, there was no significant relationship between the incidence of trauma and the number of animals per group or the sex-ratio in a group (Tables 4 and 5). From the present survey results, a prospective rearing system should be established to reduce the incidence of trauma in the cynomolgus breeding and rearing colony.