The aim of this study was to develop and validate ELISAs for quantification of HAMA-IgM and HAMA-IgG in serum of patients with ovarian cancer who enrolled in a large international randomized phase III trial of intraperitoneal Yttrium-90-labeled HMFG1 murine monoclonal antibody therapy. The capture antibody of these 2 assays was the murine antibody HMFG1, while mouse anti-human IgM-HRP or mouse anti-human IgG(Fc)-HRP served as tracer antibodies. A pool of HAMA-positive serum samples was used to prepare a series of assay standards and another pool served as reference preparation. The analytical sensitivity of the HAMA-IgM assay was 2.5 arbitrary units per mL (AU/mL) and 4.7 AU/mL for the HAMA-IgG ELISA. Diluted serum samples showed good parallelism with the HAMA-IgM and HAMA-IgG standard dose-response curves. Within-assay coefficient of variation was 7.5% for HAMA-IgM and 6.5% for HAMA-IgG. Between-assay variation was 14.2% for HAMA-IgM and 15.3% for HAMA-IgG. The developed HAMA-IgM and HAMA-IgG ELISAs show satisfactory reliability criteria (sensitivity, parallelism and precision) and are suitable for monitoring of HAMA-IgM and HAMA-IgG responses in ovarian cancer patients. These ELISAs will be used to monitor the development of HAMAs in patients who received radioimmunotherapy with murine HMFG1.