The respondent (classical) conditioning of male sexual arousal was investigated, employing penile plethysmography and 2 control procedures. Nine participants participated in three sessions, for three consecutive weeks. Each session consisted of fifteen stimulus periods and fifteen detumescence periods. Three participants participated in each of three different experimental conditioning procedures. Sexually explicit visual stimuli preselected by each participant were utilized as the unconditioned stimuli (US), and a neutral slide of a penny jar was employed as the conditioned stimulus (CS). In the first procedure, short delay conditioning, the CS was presented for 15 seconds, followed immediately by the US for 30 seconds. The second procedure was a backward conditioning procedure. In the third procedure, a random control condition, the presentation of CS and US was determined randomly. Results indicated that participants showed systematic maximum increases in penile tumescence from baseline in the short delay conditioning procedure, but not in the other two control procedures. Implications of these results to behavior therapy strategies which are based upon the conditioning of human sexual arousal are examined and discussed.