This survey for residual paralysis among rural and urban children in Central Java shows an overall rate for polio lameness of 9/10 000 children. A recent rise in reported cases of acute poliomyelitis is reflected in paralysis rate among preschool children of 22/10 000. Three quarters of cases occur before the third birthday. A majority of children below age 3 are lacking antibody titres to one or more types of polio virus, demonstrating the need for mass immunisation. A simple questionnaire detected polio cases with a sensitivity of 84%.