Case history data on 142 psychotic children were obtained using the Rimland Diagnostic Check List. A particular variety of the method known as numerical taxonomy was used to classify the children into subgroups on the basis of responses on the Check List. A comparison was made between a classification of Kanner's syndrome vs. "no Kanner's syndrome" and a classification using random classes as starting points. The "best" classification of the data was one in which 2 classes were obtained, one containing all the Kanner's syndrome children plus other early-onset, nonrelating psychotic children and the other containing children with later onset and more varied symptoms. Those attributes which significantly differentiated between the classes both in the "best" classification and in the Kanner's syndrome classification were extracted. A distinction between Kanner children and other similar children was found only for 3 specific behaviors: obsessive desire for sameness, islets of special ability, and skillful manipulation of small objects.