The pathogenicity of APMVs was evaluated with the standard pathogenicity tests used for APMV-1, namely MDT in embryonated chicken eggs and ICPI in 1-day-old chicks ( Table 1 ). The pathogenicity of the two strains of APMV-1 has been well characterized: strain BC is neurovirulent (MDT 58 h and ICPI 1.55), whereas strain LaSota is avirulent (MDT 112 h and ICPI 0.00) and is used as a vaccine strain. For the most part, APMV 2-9 were even more avirulent based on these assays than strain LaSota, regardless of their isolation sources. The one exception was APMV-3, which had a MDT value (117 h) that is similar to that of the LaSota strain, but had an ICPI value (0.53) that was higher than that of the LaSota strain (0.00), but nonetheless remained in the avirulent range. The MDT and ICPI values of other APMVs were .144 h and 0.00, respectively, consistent with being avirulent. Chicks infected with APMV serotypes 2-9 had no apparent clinical signs during the 8-day period of the ICPI test.