The treatment by a qualified sex therapist of a sexually dysfunctional couple referred by a family or marital therapist often significantly factilitates the overall therapeutic progress. When "successful," relevant effects of sex therapy include a better dyadic relationship, optimism about therapy in general, and greater willingness to change, beneficial ripple effects on other family members often occur. Resistance by partners or other family members is considered, as is the use of "unsuccessful" sex therapy as a diagnostic tool. Questions as to whether sex therapy should follow, interrupt, or proceed concurrently with family/marital therapy are discussed.