3 448 six-year-old Swedish children were screened for perceptual, motor and attentional deficits with the help of a questionnaire containing 34 yes-no questions. Epidemiological aspects of single symptoms and of groups of symptoms are presented. Boys displayed many more problems than girls. Children attending day nurseries had more problems than part-time pre-school children, particularly as regards attention and behaviour. 141 of the children- 82 with and 59 without questionnaire symptoms suggestive of so-called MBD-had been examined in an extended neuro-psychiatric study. A discriminant analysis of the questionnaire was performed for these 141 children which demonstrated that a set of 6 questions had a high discriminating capacity detecting for MBD-syndromes.