Salsolinol (1)and 6,7-dihydroxy-1,1-dimethyl-1,2,3,4-tetrahydroisoquinoline hydrobromide (2) were synthesized and their effects at adreno- and cholinoceptors investigated both in vivo and in vitro. Both 1 and 2 produced agonist effects at cholinoceptors and alpha- and beta-adrenoceptors. Neuromuscular blocking actions were evident in vitro. Compound 2 exhibited anticholinesterase properties both in vivo and in vitro. These results indicate that dopamine derivatives of this type exhibit not only sympathomimetic activity but also complex actions at cholinoceptors.