Perianal scrapings, collected by means of the N.I.H. cellophane-tipped swab, were examined from 240 patients of the James Whitcomb Riley Hospital for Children. These included 128 males and 112 females, with ages from 21 months to 18 years. They were residents of both urban and rural areas throughout the state and came from 71 of the 92 counties. Only one perianal scrapings preparation was examined from each patient. A total of 39 individuals (20 males and 19 females), or 16.3 per cent, were found to be infected with the pinworm, Enterobius vermicularis. The corrected incidence, on the basis of the examination of seven swabs, was 24.7 per cent. Eosinophil counts from both positive and negative individuals were analyzed. There seemed to be no correlation between the eosinophil count and the presence or absence of an infection with Enterobius vermicularis.