A study was undertaken to evaluate the accuracy of diagnostic laborato
ries at isolation of common avian viral pathogens. Fourteen ''unknown'
' samples were submitted to eight laboratories in seven states. All po
sitive and negative samples were guaranteed pure by SPAFAS. Virus-isol
ation results were erroneous in many cases. Based on this study, it ap
pears that protocol for virus isolation of avian pathogens should be s
tandardized throughout the United States.