Bromocriptine and lergotrile were administered to 81 patients with Parkinson disease (PD) and increasing disability despite optimal treatment with levodopa (secondary levodopa failures). Sixty-six patients were treated with bromocriptine and 53 patients were treated with lergotrile. Both groups had significantly decreased rigidity, tremor, bradykinesia and gait disturbance upon addition of bromocriptine or lergotrile to levodopa. Twenty-five patients improved at least one-stage on bromocriptine, and 21 improved at least one-stage on lergotrile. The mean dose of bromocriptine was 47 mg, and the mean dose of lergotrile was 49 mg, permitting a 10% reduction in levodopa. Bromocriptine was discontinued in 29 of 66 patients because of adverse effects, including mental changes (14 patients) and involuntary movements (9 patients). Lergotrile was discontinued in 33 of 53 patients because of adverse effects including hepatotoxicity (11 patients) and mental changes (12 patients). The results of treatment with bromocriptine or lergotrile were comparable, with patients either responding or not. Bromocriptine will shortly be available for use in PD. Lergotrile, because of the hepatotoxicity, will not.