Abstract: seasonal changes in spermatogenesis of adult tree shrews from field in Kunming,Yunnan,were investigated.Maximum aeragc diameters of seminiferous tubules are present in April (205.7 μm) and minimum in October (88.4 μm).There are highly active seminiferous epitheliums with clear epithelial cycle of 12 successive stages and typical cell associations of various stages in January and April.Regression of seminiferous tubules begins in July and there are extensive regressive changes in seminiferous epitheliums losing spermatogenic function in August and October.Similar seasonal changes in spermatozoa amount are shown in epididymis.These results suggest that a seasonal cycle of spermatogenic activity occur obviously in this species.The seasonal changes of reproduction may be regulated by local environmental factors,such as photoperiod.