Mice were immunized subcutaneously, intravenously or in a footpad with antigens prepared from a lethal strain of Plasmodium berghei yoelii. A delayed footpad swelling (DFS) reaction was observed 4 days after immunization, and was detectable at least 42 days after immunization. However, IV immunization was the least efficacious is producing hypersensitivity. Regardless of the type of antigen used for immunization, mice responded similarly when live parasites were used to elicit DFS. This study revealed that hypersensitivity depended on route of immunization and type of antigen.