A case of acute onset non-cardiogenic pulmonary edema induced by hydrochlorothiazide (HCT) is presented. Rapid recovery was obtained with supportive therapy. Leukopenia was evident during the acute phase, with rapid recovery parallel to the clinical improvement, suggesting pulmonary sequestration of granulocytes. Immunological studies including lymphocyte stimulation test with HCT and measurement of specific IgG and IgE to HCT elicited negative results. The pathogenesis of this type of reaction remains to be elucidated.