OBJECTIVES: The oral variant of the antipsychotic drug risperidone will lose patent protection at the end of 2007, which opens the market for generic variants. However, since many schizophrenic patients suffer from paranoia, some of them will be less willing to take a different drug. Switching might therefore cause non-compliance, which is in its turn the most important predictor of relapse and hospitalisation in schizophrenia. We therefore made an estimation of potential economic consequences regarding drug and hospitalisation costs when stable patients in the Netherlands currently using branded risperidone are switched to the generic version. METHODS: A simple health economic model was developed, based on published data regarding hospitalisation durations, rates of compliance, relapse, and additional relapse resulting from switching to generics. A one-year perspective was applied. RESULTS: Due to a somewhat higher relapse rate after switching to generics in the first year after the switch, total per-patient drug and hospitalisation costs were estimated to be higher for the generic product as compared to the branded product (€5110 and €4680, respectively). Sensitivity analyses showed the stability of the relative result. CONCLUSION: Switching patients who are stabilised on branded risperidone to the generic version might cause higher health care costs. The analysis is dependent on assumptions, but given their evidence-based character, there is sufficient reason to believe that the relative result will hold in countries where only a little difference will exist between the price of branded and generic risperidone after the patent expiry.