Revised versions of diagnostic manuals, the International Classification of Diseases (ICD-10), and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) all operate with several subgroups in the autistic spectrum. Five of the subgroups are identical in the two manuals, but ICD-10 contains five in addition. 132 children were diagnosed using ICD-10, DSM-IV, DSM-III-R, the Childhood Autism Rating Scale (CARS), and the Autistic Behavior Checklist (ABC). Five out of ten alternative subgroups of Pervasive Developmental Disorders (PDD) were identified in a population of developmentally impaired children. These subgroups were the same in the two manuals; the additional ones in ICD-10 were not identified. With the exception of the groups Disintegrative Disorder and Rett syndrome, significant differences were found between all the subgroups within the PDD spectrum and between the PDD group and the non-PDD group. Some problems connected with the guidelines in the ICD-10 manual are discussed.