Tests of handedness were carried out with 34 autistic children aged from 4 years 10 months to 18 years 11 months, and with sex-, age-, and IQ-matched retardates and sex- and age-matched normals. There were no significant differences between the groups on frequency of handedness, degree of righthand usage, or degree of dominant-hand usage. There was however a significant increase in the variance of dominant-hand usage from normals and retardates to autistics. These results were taken to indicate that earlier reports of handedness differences in young autistic children may reflect a developmental lag rather than a specific etiology of autism. Some support for this hypothesis was found from a comparison of age-trends between the groups. The relationship of such a developmental delay to the etiology of autism was discussed. © 1978 Plenum Publishing Corporation.