Lymphocyte blastogenic responses against food allergens in dogs with food hypersensitivity were evaluated in this study. Eleven dogs with food hypersensitivity, based on food elimination and oral food provocation tests and allergic responses to food allergens, were examined by various tests such as intradermal testing, antigen-specific IgE testing, and lymphocyte blastogenic responses. The number and kinds of food allergens identified as positive by these tests were compared with the offending food allergens that were found in an oral food provocation test. In 9 (82%) of the 11 dogs with food hypersensitivity, there was close agreement for positive allergens between the results of lymphocyte blastogenic responses and oral food provocation test; however, there was little agreement for intradermal and IgE testing of the positive allergens with those of the oral food provocation test (11% and 31%, respectively). In the 9 dogs, the stimulation indices of lymphocyte blastogenic responses increased to 2.0-10.1 upon food provocation but decreased significantly to 0.7-1.4 upon feeding the elimination diet until clinical signs disappeared. These results indicate that lymphocyte blastogenic responses may fluctuate because of exposure to offending food allergens in dogs with food hypersensitivity. Lymphocytes reactive to food allergens may play an important role in the pathogenesis of food hypersensitivity in dogs.