The transfer of 14C-bromocriptine across the blood-brain barrier was studied in 10 patients using the double indicator single injection method. The extraction (E) of bromocriptine was 8 % (quartiles: 6 and 14 %). Based on the results the cerebral uptake velocity of bromocriptine was calculated assuming constant arterial drug concentration. Its T 1/2 was found to be 12--24 minutes, depending on the tissue-blood partition coefficient.