Electrodermal activity to auditory stimuli was compared in 20 autistic children and their matched retarded and normal controls (N = 80). The autistic children were virtually indistinguishable in individual features of electrodermal activity from controls when both chronological and mental age comparisons were accounted for. When patterns of activity were considered globally, both autistic and retarded children could be distinguished from one another and from normal controls. However, in some respects autistic and same-aged normal children were alike--both showed sensitization to 70-dB tones and both had a higher incidence of children with larger left- than right-hand responses, interpreted as evidence of focused attention under left hemisphere control.