The microdissection technique was used to study otoconial membrane from 30 human infants ranging from newborn to 2 years of age. Both saccular and utricular membranes were quite variable in overall shape. During the neonatal period, the gelatinous layer of the otoconial membrane appears to thicken and become less adherent to the macular surface than in the fetal period. In many infants older than 6 weeks, otoconial membranes were found at autopsy to be completely dislodged from the maculae, with abnormally large saccular otoconia present in four specimens. Fourteen of the infants studied died of sudden infant death syndrome and 16 died of other causes. The incidence of detached otoconial membranes was approximately the same in both groups. Although the majority of these membranes were apparently dislodged post mortem, the present findings suggest that otoconial membranes are susceptible to pathological alteration due to disease or head trauma.