Biochemical, histochemical and behavioural experiments suggest that many ergot drugs possess dopamine (DA) agonistic activity at the postsynaptic DA receptors. It seems likely that this action of bromocriptine and Lergotrile explains their unique anti-parkinsonian properties. Studies on DA-sensitive adenylate cyclase reveal only 10—30% increases of adenylate cyclase activity in striatum. It may, thus, be that small increases in adenylate cyclase activity may be sufficient to produce enhancement of DA neurotransmission in the brain. In agreement it was found that the increase caused by agroclavine in adenylate cyclase activity is significantly enhanced in denervated striata. With low concentrations of ergot drugs a positive interaction was found with DA at the level of the adenylate cyclase. Of all the ergots tested for DA agonistic activity agroclavine and elymoclavine were found to be the most potent in all models studied.