Investigations on the fecal transmission of T. spiralis have been carried out using fox cubs and albino rats as donors, while swine, albino rats and fox cubs served as recipient hosts. The feces of experimentally infected animals have been examined by the Baermann technique to ascertain the number of larvae eliminated. The following factors were found to affect transmission: 1) time interval between infection and passage of feces by donor, 2) relative immunity of donor, and 3) number of trichinae ingested by the donor. About 95% of the larvae passing through the intestinal tract of the donors were recovered from feces eliminated within 24 hours after ingestion. Immune animals eliminated a larger percentage of the administered trichinae than did nonimmune animals.