An investigation of lower limb motor disorders among school-age children in Niger has shown a prevalence rate of seven per thousand in this age group. Sequelae of poliomyelitis, the major group among these disorders, show no significant difference according to sex or to school attendance status. Eight per cent of children suffering from poliomyelitis sequelae are unable to work and a further eight per cent need crutches or other aids. Patient histories indicate that over 90% of cases occurred before the child's fourth birthday. Extrapolation from the observed data indicate a tentative annual incidence rate for paralytic poliomyelitis in the order of 45 per 100,000, a figure seven to ten times higher than the figures gathered from routine notifications of poliomyelitis in Niger. The total number of those unable to walk unaided among children under 15 can be estimated in 1981 at 1600, half of whom are unable to walk at all. Trauma to peripheral nerves after intramuscular injections, usually of quinine salts, is second only to poliomyelitis as a cause of lower limb motor disorders.