Protein‐A rich staphylococci were used to develop an agglutination assay for the detection and quantitation of avian reticuloendotheliosis virus (REV) and Herpes virus of turkeys (HVT). Rabbit anti‐REV or anti‐HVT were used to coat the staphylococci and these reagents were mixed with REV or various other viral antigen preparations. An agglutination titer was determined for antigen preparations of varying purity and the results indicated that in addition to being rapid, this assay allows the detection of as little as 0.3 to 0.5 μg of partially purified viral antigens. No crossreactivity was observed with the two antisera and the various antigen preparations. This study also confirmed the reports in the literature that chicken immunoglobulins do not bind to protein‐A of the Cowan I strain of Staph, aureus.