Conceptual issues and relevant literature pertaining to the interface between marital and sexual function are reviewed. The procedure and results of a treatment outcome study are described. Couples complaining of sexual difficulties received both sex therapy and marital therapy in a balanced, cross-over design. Results on measures of sexual interaction and marital happiness revealed a complex pattern of treatment by sex effects. Sex therapy resulted in more change than marital therapy for both men and women in their dissatisfaction with the frequency of sexual activity. For women, sex therapy produced greater improvement in their average level of sexual enjoyment, whereas men showed a trend favoring change in response to marital versus sex therapy on this measure. Self-acceptance of sexual enjoyment revealed a superior effect for sex therapy with women, while marital therapy again proved more effective in this regard for men. Sex therapy demonstrated a greater impact on mate acceptance in sexual enjoyment for men, while women evidenced a differential treatment response in favor of marital therapy in this regard. Finally, in terms of overall marital happiness, both men and women showed a strong initial response to treatment, regardless of whether it was sexual or marital therapy. Implications of these findings for clinical treatment and future research are discussed.