Pharmacokinetic studies were carried out with 9 3H-labeled ergot alkaloids (dihydroergotamine, dihydroergotoxine, dihydroergostine, dihydroergocornine, dihydroergovaline, dihydroergonine, ergotamine, 1-methyl-ergotamine, and bromocriptine). Each drug was administered to 6 subjects in a randomized cross-over design as single oral and i.v. doses. Plasma levels and urinary excretion of 3H-labeled material were analyzed on a phenomenological basis by non linear regression as a sum of exponentials. All substances showed the highest plasma concentration about 2 h after oral administration (range 1.0-2.7 h). The mean invasion half-life was 0.5 h (range 0.32-1.12 h). The mean elimination half-lives ranged from 1.4-6.2 h for the .alpha.-phase and from 13-50 h for the .beta.-phase, the longest values being observed with bromocriptine. A quotient of absorption was calculated from cumulative urinary excretion data after oral and i.v. adminstration. Values between 25-30% were found for most dihydrogenated drugs, i.e., dihydroergotamine, dihydroergotoxine, dihydroergostine and dihydroergocornine; the only exceptions were dihydroergovaline and dihydroergonine which were less well absorbed. Ergotamine and 1-methyl-ergotamine had an absorption quotient of about 2/3 and bromocriptine was nearly completely absorbed.