An ELISA was used to measure the Cryptosporidium-specific IgA, IgG, and IgM antibody levels in serum, stool, and duodenal fluid of 15 Filipino children. Antibody levels were measured on admission to the hospital, 1 week later, and at a 6 week follow-up examination. Delayed type hypersensitivity skin tests were used to assay cell mediated immunity (CMI), iron status was measured by serum iron tests and total iron binding capacity, and the degree of malnutrition was determined by clinical examination. Antibody response to Cryptosporidium was qualitatively and quantitatively strong and maintained over time. All subjects showed impaired CMI early with some reconstitution after 6 weeks. All subjects showed some degree of malnutrition and/or depleted iron status.