To examine the performance of a self-report diary to assess psychosexual function in hypogonadal men, 2 groups of eugonadal men and 2 groups of hypogonadal men were asked to record and score parameters for sexual desire, sexual enjoyment, sexual performance, sexual activity, and positive and negative moods daily for 7 days before a clinic visit (data set 1 and 2). The hypogonadal men were also assessed after testosterone replacement and some of the eugonadal men were studied while they were on placebo treatment. In this retrospective analysis, sexual function parameters (sexual desire, performance, and activity score) in the diary discriminated between the hypogonadal and eugonadal men with all measures significantly lower in hypogonadal men (all parameters P <.0001). Significant improvements in sexual desire and performance as well as sexual activity scores (P <.0001 for all parameters) in hypogonadal men after testosterone treatment were readily detected within 30 days. Mood and functional parameters did not show any change over time in eugonadal men on placebo treatment. The mood parameters assessed by the diary showed an excellent correlation with those assessed by the Profile of Mood States. Mood parameters were not clearly different between eugonadal and hypogonadal men at baseline. With testosterone treatment positive mood parameters were significantly increased (P <.0028 and.0001 set in data 1 and 2, respectively), and negative mood parameters improved in hypogonadal men (P <.0003 in data set 2). We conclude that this simple self-report diary is useful in assessing the sexual function and mood profile of hypogonadal subjects in clinical research.