With the majority of current information being derived from short-term clinical trials, the impact of atypical antipsychotics during maintenance treatment of schizophrenia is of considerable interest, although only limited data are available at present. The present report is an analysis of data that are available up to 156 weeks after the start of an open-label extension (OLE) phase of three, double-blind randomized trials in quetiapine-treated patients who responded to an initial 6-week treatment period. The mean daily quetiapine dose (range 150-750 mg) was 439.5 mg for patients included in the brief psychiatric rating scale (BPRS) and 438.5 mg for patients included in the clinical global impression (CGI) analyses. The initial mean acute phase BPRS total score (40.67; n=258) and CGI severity of illness score (4.81; n=259) were reduced at the start of the OLE to 13.94 and 3.00, respectively. After 156 weeks, endpoint scores were 9.04 for BPRS and 2.43 for CGI severity of illness. Although limited by patient attrition, these OLE data suggest that an initial beneficial response with quetiapine treatment can be maintained over a long-term period.