The proposed research will extend and expand the study now in progress of residual effects of long-term chronic administration of delta 9-THC on primate social behavior and stress-response neuroendocrine systems. Drug exposure will be extended to one year (instead of six months) and post-drug observations to six months (instead of two months), followed by extensive comparative microneuropathology of brains of treated vs. cagemate control subjects. Endocrine parameters will be extended to include plasma level of estrogen, progestins, testosterone, and possibly luteinizing hormone. Daily oral administration of THC will be at a level comparable to human use and primate subjects will be pubertal or young adults. The proposed extension of this study appears warranted in view of 1) the demonstrated effectiveness of the test systems in acute and short-term chronic studies with THC recently completed in our laboratories, and 2) recent suggestive evidence of THC or cannabis- induced cerebral atrophy and gonadal-reproductive hormonal changes in both human and non-human primates after long-term chronic exposure.