The biological characteristics of an avian paramyxovirus isolate, strain GPMV/QY97 1 showing pathogenicity to geese, were characterized. The results were as follows: spherical virons 121 250 nm in diameter and surface covered with spikes were observed under electron microscopy. The virus could agglutinate chicken erythrocyes, and the hemagglutination reaction could be inhibited by standard antiserum of paramyxovirus 1. So the virus was identified as paramyxovirus 1. The morbidity of 1,14,28,48 day old...