The effect of 80%-90% neuroleptic dose reductions on neuropsychological function in schizophrenic and schizoaffective patients was examined in a prospective study. A neuropsychological battery was administered in the week prior to neuroleptic reduction followed by retesting at least 6 weeks postreduction. Patients were retested only if they did not relapse after reduction. The design allowed neuropsychological changes due to neuroleptic medications to be assessed independently of general clinical change. Neuropsychological performance was generally stable and unchanging. However, there was a trend toward significant improvement on a dichotic digits task based in improvement in left ear accuracy. Negative symptoms diminished after reduction. Compared with a normal control group, schizophrenics' initial laterality index showed a significantly exaggerated right ear advantage (REA); after reduction, the REA was no longer different from controls. The findings indicate that neuropsychological changes in a small sample of older nonrelapsing chronic schizophrenics are modest. The data suggest that neuroleptics may impair right hemisphere functions in some patients.