Lergotrile is an ergot alkaloid clinically effective in the treatment of Parkinson’s disease. The in vivo dopaminergic effects of lergotrile are similar to those produced by the direct acting dopaminergic agonists apomorphine or L-DOPA. Like apomorphine or L-DOPA, lergotrile decreases prolactin secretion, produces stereotyped behavior in intact rats, and causes contralateral rotation in rats with uniIateral 6-hydroxydopamine lesions of substantia nigra. However, unlike apomorphine or L-DOPA, lergotrile does not activate dopamine sensitive adenylate cyclase in vitro. Side effects of lergotrile included exacerbation of hallucinations, dyskinesias, hypotension, and alterations in liver function tests. Although lergotrile, when added to levodopa, has a definite antiparkinsonian effect, the incidence of adverse effects, particularly hepatotoxicity, makes it unlikely that this ergot alkaloid will become widely available for the treatment of Parkinson’s disease.