In 8 male rats instrumental responses reinforced by contact with an estrous female with an intact or a surgically closed vagina were investigated. Contact with the female lasted until the end of the mount bout. It was observed that neither the rewarding value of the mount bout (expressed by the duration of the response) nor its arousing properties (expressed by the rate of bar presses) depended on the quality (mounts or intromissions) or quantity of the copulatory events of which it was composed. It is suggested that the temporal patterning of copulatory behaviour in male rats depends on fluctuations of sexual reward. This sexual reward can be a result of both genital stimulation as well as the performance of mounting under the influence of sign stimuli coming from the estrous female.