Surprisingly little is known about the course of intellectual development in children with infantile psychosis. Kanner (1943; Kanner and Lesser, 1958) has stated explicitly in several papers that “even though most of these children are initially considered feeble-minded, they are all unquestionably endowed with good cognitive potentialities, which are masked by the basic disorder” (original italics—Kanner and Lesser, 1958). The expectation would seem to be that the child's IQ, should fluctuate with the course of the psychosis, particularly the autistic aspects, but this has not been tested. It has been suggested (Anthony, 1958) that an intelligence test result in a young child with infantile psychosis is most unreliable and virtually meaningless if the child is without speech. Perhaps because most investigators have shared this view, neither of the two major follow-up studies of children with infantile psychosis, that of Kanner's cases (Eisenberg, 1956; Eisenberg and Kanner, 1956; Kanner, 1943 and 1949; Kanner and Eisenberg, 1955; Kanner and Lesser, 1958) and that of psychotic children seen by Creak (1962, 1963a and b) has included information on IQ changes.