Clinicians have long associated depression with alterations in sexual function, predominantly loss of sexual interest. In a longitudinal study measuring self-report, behavioral, and nocturnal penile tumescence variables before and after treatment with cognitive behavior therapy in an unmedicated sample of 40 outpatient depressed men, we found, contrary to expectation, that sexual activity per se was not reduced during the depressed state. Rather, loss of sexual interest appeared to be related to the cognitive set of depression, ie, loss of sexual satisfaction that then improved with remission from depression. Depressed men were heterogeneous, however, with respect to sexual behavior, eg, an anxious and more chronically depressed subgroup of men who did not have remissions with cognitive behavior therapy reported increased sexual interest and sexual activity. Also, contrary to expectation, nocturnal penile tumescence abnormalities in depressed men did not reverse when measured in early remission, nor did nocturnal penile tumescence measures correlate significantly with behavioral measures of sexual function. Nocturnal penile tumescence alterations in depression may thus be similar to other persistent electroencephalographic sleep abnormalities seen in depressed patients in remission, in being more trait-like than statelike.