This multicenter, double-blind, randomized study evaluated the efficacy, safety and functional effects of two atypical antipsychotics, amisulpride and risperidone, in patients with chronic schizophrenia (DSM IV) with a recent worsening of symptoms. It was planned as a non-inferiority trial. 309 patients received amisulpride (400-1,000 mg/day) or risperidone (4-10 mg/day) for six months. Amisulpride was demonstrated to be not inferior to risperidone with respect to the decrease in Positive and Negative Syndrome Scale (PANSS) total score from baseline (90% 2-sided confidence interval (-5.6; 4.0)). Symptomatic improvement measured with the Brief Psychiatry Rating Scale (BPRS), the PANSS positive subscale, and the Bech Rafaelsen Melancholia Scale was similar in both groups. Amisulpride was significantly (p <.05) superior to risperidone in terms of response (>/=50% improvement in PANSS and BPRS total scores or "very much/much improved" on the Clinical Global Impression Scale) and also demonstrated better functional effects and subjective response. Both treatments were well tolerated and had a similar low incidence of extrapyramidal symptoms; however, amisulpride was associated with less weight gain and endocrine/sexual symptoms.