In September, 1930, Dr E. C. Faust brought back from the Coto Region of Northern Panama two young female spider monkeys (Ateles geoffroyi). On December 11th one of these died from an experimental infection of Strongyloides stercoralis, and at autopsy was found to be very heavily infested with lice. Previous to this date the monkey had been handled a number of times but no lice noticed, although the two monkeys had frequently been observed carefully examining each other for external parasites. It is believed that the subsequent separation of the two (November 22nd) combined with the victim's illness allowed the lice to multiply at a prodigious rate. The hairs practically all over the body were found to bear nits, frequently as many as three or four per hair. Only a few lice have ever been found on the other monkey in spite of several careful examinations.