Acetylcholinesterase (AChE) from erythrocytes was solubilized by Triton X-100. Size and charge heterogeneity of AChE was investigated by polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing (IEF) in polyacrylamide gels in the presence of 0.5% (v/v) Triton X-100. There were no interindividual differences in these parameters in 46 psychiatric patients (schizophrenia, major affective disorder, personality disorder, dependency, dementia) and controls. The specific activity of solubilized AChE did not discriminate between controls and patients or between the diagnostic subgroups.