A series of trials was conducted to determine the effects of upper intestinal tract damage upon the absorption of labeled zinc and oleic acid used as examples of mineral and fatty nutrients. The protozoan parasite Eimeria acervulina, which attacks the anterior portion of the chicken intestine, was used to produce the intestinal damage. The infection caused growth retardation on the seventh through tenth days post-inoculation and visible damage to the lining of the upper one-third of the intestinal tract during the period from 5 to 10 days post-inoculation. Increased absorption of orally administered 65Zn and 131I-labeled oleic acid occurred on day 1 and from days 14 through 21 post-inoculation, whereas greatly decreased absorption of both labeled nutrients was observed on days 5 through 10 post-inoculation. Both oleic acid and zinc absorption were severely and equally depressed by E. acervulina infection. This was contrasted with E. necatrix infection in which zinc absorption was much more severely affected than oleic acid absorption.