The present report is an extension of a previous study of the accessory sex gland function in normal young (20-25 years) and middle-aged (50-55 years) men. In the same individuals, the basal and in vitro stimulated activities of the sperm adenylyl cyclase were determined. A high degree of individual variation existed in both basal and Gpp(NH)p-, forskolin- and acetate-stimulated sperm adenylyl cyclase, and no significant difference could be demonstrated between the means of the age groups. Furthermore, no significant correlation existed between the concentrations of the glandular secretory products (prostatic acid phosphatase, citric acid, zinc, spermine, spermidine, putrescine, fructose and prostaglandin E) in the ejaculate and the activity of the sperm adenylyl cyclase. Furthermore, the number of morphologically abnormal sperm cells in the ejaculate did not influence the activity of the enzyme. No inverse correlation existed between the magnitude of basal activity and the relative response to Gpp(NH)p, forskolin or acetate suggesting that the variation in the enzyme could not be explained by its partial desensitization by seminal plasma constituents during the liquefaction period. A lack of correlation between the response of the enzyme to Gpp(NH) p and forskolin on the one hand and acetate on the other, implied that these drugs activate the enzyme through different mechanisms.