OBJECTIVES: The quality of life (QoL) of 44 men with HRPC and 37 partners (primary caregivers, most residing with the patient) was assessed in a multicenter Phase II trial of docetaxel, estramustine and low dose hydrocortisone (CALGB 9780). A secondary objective was to test the feasibility of assessing partners' QoL in a cooperative group setting. PATIENTS AND METHODS: Patients and partners were separately interviewed by telephone at baseline, two, four and six months by a single trained research interviewer. Patients' QoL was measured by the FACT-P, Mental Health Inventory-17 (MHI-17), Brief Pain Inventory (BPI), a two-day log of pain medications, and the OARS for co-morbid conditions. Partners' QoL was measured by the MHI-17, Caregiver Burden Interview, and co-morbid conditions. RESULTS: The QoL study refusal rates were low for patients (4%) and partners (3%). Although patients tended to experience greater treatment side effects in the first two months (FACT Physical Well-Being item, P = 0.057), their cancer-specific emotions (e.g., worrying about worsening health) significantly improved at two and four months (FACT-Emotional Well-Being, P = 0.003, P = 0.03, respectively), as did their prostate cancer-specific physical problems (e.g., urination, pain), at two and four months (FACT-P, P = 0.001, P = 0.005, respectively). Partners' anxiety significantly decreased over time (MHI, P < 0.05). Patients' quality of life at two months was significantly related to their clinical response (FACT-P total and prostate cancer-specific problems, P < 0.05), and their clinical response was significantly related to a decrease in their partners' anxiety at two months (MHI, P < 0.05). CONCLUSIONS: Despite feeling worse from side effects, patients' prostate cancer-specific problems and emotional state significantly improved in the first four months of treatment. With treatment significantly affecting both patients' and partners' lives. and the successful assessment of partners' QoL, QoL of both patients and partners could be used as important endpoints in selected clinical trials.