Two methods for collecting blood for measuring antibody activity of Pasteurella multocida were compared. Whole blood was collected on filter-paper strips, dried for 48 hr at room temperature, and then stored in sealed plastic bags at 4 C. Blood was also collected in the usual manner with a needle and syringe, and serum was harvested and stored at -20 C until tested. Eluates of whole blood, obtained by overnight elution of two 4.8-mm discs in 200 microliters of buffered saline at 4 C, were compared with conventionally harvested serum for antibody activity by enzyme-linked immunosorbent assay (ELISA). Paired samples, taken from the same bird at the same time, showed no significant difference (P less than 0.05) in antibody activity as measured by absorbance when the disc-elution process itself was considered to be a 1:20 dilution. It was concluded that eluates of blood, derived from whole blood dried on filter-paper strips, may be used as an alternative to sera in ELISA for measuring P. multocida antibody activity.