OBJECTIVE: Androgen deprivation therapy (ADT) is the primary treatment for advanced prostate cancer (CaP). There is growing evidence that ADT negatively affects men's psychosocial well-being (e.g., causing sexual dysfunction, bodily feminization) and physical health (e.g., increasing the risk of osteoporosis and metabolic syndrome). Although strategies for managing the majority of side effects exist, it is not clear that patients are benefiting from this knowledge. METHODS: Seventy-nine newly prescribed ADT patients and 54 of their partners were given a checklist of various common and uncommon ADT side effects. They were asked to indicate the drug side effects that they had heard of or anticipated. RESULTS: Both patients and their partners were poorly informed about the side effects of luteinizing hormone-releasing hormone (LHRH) agonists used for ADT. More than 70% did not know that anemia, memory problems, loss of body hair, and depression can occur following treatment. Over 50% were unaware of significant potential side effects such as reduced muscle mass, osteoporosis, increased fracture risk, weight gain, genital shrinkage, and gynecomastia. Concurrently, more than 20% mistakenly anticipated dizziness and itching. CONCLUSION: The lack of awareness of ADT side effects may partially explain why ADT currently results in significant decreases in the quality of life of patients and their partners. Patients uninformed about side effects do not engage in behaviors to prevent or reduce the risk of adverse effects. Improved efforts to educate patients about treatment side effects and coping strategies may result in improved psychosocial and physical health for CaP patients undergoing ADT.