In 1967 all children who entered ordinary schools on the Isle of Wight had a special school-entrant medical examination. The validity of this examination was demonstrated by (a) comparison with a psychological battery; (b) study of children with known disorders ; and (c) follow-up. The investigation suggests that at least 6% of children have a significant neurodevelopmental disorder. A comprehensive school-entrant examination increases the value of the school doctor's work.