Nocturnal sleep patterns were registered from 6 parkinsonian patients treated with bromocryptine, ("-Br-L-ergocryptine, C.B.-154) a dopamine-like agonist. No significant differences in their sleep patterns were found in comparison with patients treated with L-dopa. Since bromocryptine acts direct on the dopaminergic receptor sites, it is suggested that the disturbed EEG sleep patterns in parkinsonian patients cannot be explained by altered dopaminergic or serotoninergic effects whether pre- or postsynaptic.