The diagnosis of strongyloidiasis relies upon the identification of the parasite in stool samples. In 1981, a serologic assay was developed, which was useful in the diagnosis of strongyloidiasis in the immunocompetent host. In the present study, we evaluated the enzyme-linked immunosorbent assay (ELISA) in patients with hematologic malignancies. Between April 1995 and December 1998, sera from 164 consecutive patients were tested for the presence of IgG antibody to Strongyloides stercoralis. Patient was considered uninfected after at least three negative stool examinations. The prevalence of strongyloidiasis was 13%. The underlying diseases were acute leukemia in 21% and lymphoma in 52% of the patients. The majority of the patients were receiving chemotherapy (93%) and steroids (76%). The sensitivity, specificity, and positive and negative predictive values were 68%, 89%, 48%, and 95%, respectively. The ELISA may be an excellent assay to rule out the diagnosis of strongyloidiasis in patients with hematologic malignancies.