We examined the influences of regular sexual activity and marital status on salivary testosterone levels in healthy adult Japanese men. Forty-four men (20-66 years) collected their saliva thrice a day (0900-1000, 1300-1400, and 1700-1800). The testosterone levels at each collection time negatively correlated with the ages of the participants; therefore, residual testosterone levels were used for analyses after correcting for age by linear regression. The testosterone-lowering effect of marriage was marginal and the regular sexual activity more strongly associated with lower testosterone levels in morning saliva. The possible neurofeedback systems underlying the phenomenon are discussed. © 2006 Japan Ethological Society and Springer.