The authors have studied by high field MR (Signa 1.5 T, GE) 11 patients with known Parkinson's disease and 19 normal controls. In all cases the widths of the pars compacta were measured by optical densitometry in T2-weighted images (gradient-echo TR 2600, TE 80). In Parkinson's patients the compactae of the nigra were found to be significantly thinned (p less than 0.01) which may be of importance for the discussion of the physicopathology and clinic of the extrapyramidal disease.