PURPOSE: To study the sexual effects of the 2-year adjuvant goserelin (Zoladex [Zeneca AB, Södertälje, Sweden]) alone, tamoxifen alone, and Zoladex and tamoxifen in combination (ZT) versus no adjuvant endocrine therapy among premenopausal breast cancer patients with or without chemotherapy in a controlled clinical trial (a European multicenter trial: Zoladex in Premenopausal Breast Cancer Patients). PATIENTS AND METHODS: This prospective study examined several aspects of sexuality through the use of self-administered questionnaires, which were completed by patients at seven points of assessment for 3 years after randomization. RESULTS: Patients treated with chemotherapy had a higher level of sexual dysfunction than did patients who received no systemic treatment. The addition of endocrine treatment did not alter this result. In contrast, among patients who did not receive chemotherapy, Zoladex and ZT produced a significantly higher level of dysfunction from 1 to 2 years after inclusion, as compared with those who received no endocrine treatment. Tamoxifen alone did not produce side effects. After termination of endocrine treatment, sexual dysfunction began to diminish. Those with chemotherapy had high and frequently increasing levels of dysfunction even after 2 to 3 years of independent of endocrine treatment. Zoladex had a negative effect on sexual fear, which was reduced by the addition of tamoxifen. CONCLUSION: Zoladex increased sexual dysfunction during treatment among patients without chemotherapy, but the disturbances of sexual functioning were reversible. The use of adjuvant chemotherapy was associated with continued sexual problems, even at 3 years after randomization.