The induction of oral tolerance for DTH responses to ovalbumin is impaired in protein-deprived mice. This may be via the effects of protein malnutrition on short-lived Ts cells, but an alternative explanation is that the gut handling of antigen is abnormal. We have attempted to transfer tolerance from protein-deprived and control mice to naive recipients by using spleen cells, collected 7 days after an OVA feed at a time when Ts cells should be present, or by using serum, collected 1 hr after feeding, which should contain tolerogenic, 'gut-processed' antigen. Suppression of DTH was transferred with 7-day spleen cells and with 1-hr serum from normal, protein-sufficient mice. Mice that received spleen cells from protein-deprived donors were not tolerant, but suppression was readily transferred with serum from deprived mice, indicating that their capacity for intestinal antigen processing was normal. Furthermore, the quantity of absorbed antigen in the serum 1 hr after feeding was similar in both protein-deprived and normal groups. The results obtained are consistent with the hypothesis that short-term protein deprivation depletes a population of short-lived Ts cells which control DTH oral tolerance.