Recent meta-analytic work suggests atypical antipsychotics may be clinically superior to conventional antipsychotics, although many stable patients remain on conventional antipsychotic treatment. A long-acting atypical agent may benefit patients in realms of both advanced medication delivery and mechanism of action. In a multicentre, open-label study of 725 patients with schizophrenia or schizoaffective disorder, patients received 25–75 mg of long-acting risperidone every 2 weeks for up to 50 weeks, with performance of standard safety and efficacy assessments. Data are presented on stable patients receiving oral conventional antipsychotics at study entry. In the 46 (6.3%) stable patients receiving oral conventional antipsychotics (followed between 6 months and 1 year; mean 468 days), mean (SD) Positive and Negative Syndrome Scale (PANSS) total score improved from 73.1±17.2 to 64.5±18.2 (P=0.0006). Clinical improvement of ≥20%, ≥40% or ≥60% reduction in PANSS total score occurred in 49%, 29% and 10% of stable patients, respectively. Extrapyramidal Symptom Rating Scale subjective ratings and objective physician ratings (parkinsonism) decreased significantly (P<0.05). The hypothesis that switching stable patients treated with oral conventional antipsychotics to long-acting risperidone may result in significant improvements in psychiatric and movement disorder symptomatology merits further investigation.