Effects of antiparkinsonian medication on the rabbit syndrome (RS) and accompanying parkinsonian symptoms were studied in 5 schizophrenic inpa-tients receiving long-term antipsychotic medication. All patients showed early improvement of RS following additional treatment with trihexyphenidyl or biperiden, with a significant reduction in the RS score also observed. The improvement of RS paralleled improvement of the parkinsonian symptoms, with the score of the Simpson-Angus rating scale significantly reduced. Our data provide further evidence that the underlying mechanism of RS is similar to that of acute forms of drug-induced parkinsonism.