Use of non-steroidal antiandrogens decreased overall survival and increased clinical progression and treatment failure. Subgroup analyses showed that non-steroidal antiandrogens, compared with castration, were less favourable for overall survival, for clinical progression and for treatment failure in men with metastatic disease. Participants receiving antiandrogens were also more likely to stop treatment as the result of side effects. The risk of suffering breast pain, enlargement of breast tissue or symptoms of physical weakness was also increased with non-steroidal antiandrogens. The risks of feeling intense heat with sweating and rapid heartbeat and of bleeding, the need to get up in the night to urinate, loss of sexual interest, extreme tiredness and the need to urinate more often than usual were increased with castration. No difference was noted for other side effects. The effect of non-steroidal antiandrogens on cancer-specific survival and biochemical progression remained unclear.