We investigated serum creatine phosphokinase (CPK) and associated parkinsonic (SEPS) and dyskinetic (AIMS) movements in 32 hospital admitted acute catatonic patients. Thirty-two (N = 24 without neuroleptics on admission) catatonic patients were compared with 32 non-catatonic dyskinetic psychiatric patients, 32 non-catatonic non-dyskinetic psychiatric patients and 32 healthy controls. CPK was significantly higher (P = 0.015) in catatonics (mean 255.75, S.D. +/- 226.54) than in healthy controls (38.6, +/- 27.4) and non-catatonic non-dyskinetic psychiatric patients (57.1, +/- 120.8) whereas there was no significant difference between catatonics and non-catatonic dyskinetic psychiatric patients (453.4, +/- 128.5). There were significantly positive correlations between CPK and AIMS, as well as significantly negative correlations between CPK and SEPS, in all three groups. Our results suggest that increased serum CPK in catatonia may be related to occurrence of dyskinetic movements. Furthermore, we were able to distinguish a parkinsonic (low CPK, low AIMS, high SEPS) and a dyskinetic (high CPK, high AIMS, low SEPS) subtype in catatonia.