Sexual dysfunction, a common side effect of antipsychotic medications, may be partly caused by dopamine antagonism and elevation of prolactin. In QUALIFY, a randomized study, aripiprazole once-monthly 400mg (AOM 400), a dopamine D-2 receptor partial agonist, showed noninferiority and subsequent superiority versus paliperidone palmitate (PP), a dopamine D-2 receptor antagonist, on the Heinrichs-Carpenter Quality-of-Life Scale (QLS) in patients with schizophrenia aged 18-60 years. Sexual dysfunction (Arizona Sexual Experience Scale) and serum prolactin levels were also assessed. Odds for sexual dysfunction were lower with AOM 400 versus PP [week 28 adjusted odds ratio (95% confidence interval), 0.29 (0.14-0.61); P=0.0012] in men [0.33 (0.13-0.86); P=0.023], women [0.14 (0.03-0.62); P=0.0099], and patients aged 18-35 years [0.04 (<0.01-0.34); P=0.003]. Among patients shifting from sexual dysfunction at baseline to none at week 28, there was a trend toward greater improvement in the QLS total score. The mean (SD) prolactin concentrations decreased with AOM 400 [-150.6 (274.4)mIU/l] and increased with PP [464.7 (867.5)mIU/l] in both men and women. Six PP-treated patients experienced prolactin-related adverse events. In addition to greater improvement on QLS, patients had a lower risk for sexual dysfunction and prolactin elevation with AOM 400 versus PP in QUALIFY.