Although many children with early infantile autism cannot maintain attention to externally imposed tasks, they may continue a repetitive behavior of their own choosing for long periods of time. This study examined the performance of autistic and mental age matched normal children on a Continuous Performance Test of sustained attention. Results suggest that autistic children's difficulties in sustaining attention on imposed tasks may be attributable partly to a developmental delay and partly to the motivational contingencies of task rather than to a primary impairment in the ability to sustain attention.