The systemic fungal organism, Blastomyces dermatitidis causes blastomycosis in animals and humans. This study was designed to evaluate antibody detection in 55 serial serum specimens from 9 dogs with blastomycosis using B. dermatitidis yeast lysate antigens produced from two human isolates (B5896; B5931) and two dog isolates (ERC-2; T-58) with the indirect enzyme linked immunosorbent assay (ELISA; peroxidase system) to determine an optimal lysate antigen(s) for use in the ELISA to detect antibody in the dog serum specimens. The mean absorbance values when the lysate antigens were compared with respect to their ability to detect antibody in the day 0 sera from the 9 dogs were 1.024 (ERC-2), 1.351 (B5896), 1.700 (B5931) and 2.084 (T-58) respectively. All of the reagents exhibited a high level of sensitivity and in all instances the amount of antibody declined as the time interval post-treatment increased, but the T-58 lysate prepared from the dog isolate from Tennessee was the optimal reagent. We continue to evaluate antigens for B. dermatitidis antibody detection in different immunodiagnostic assays.