A viral agent, identified as a herpesvirus and tentatively called 'inclusion body disease of cranes' (IBDC), was isolated from captive cranes involved in a die-off at the International Crane Foundation near Baraboo, Wisconsin. Preliminary animal susceptibility tests, based on experimental infections, suggested that White Pekin ducklings up to 17 days old and adult coots were susceptible to the IBDC virus whereas 16-day-old White Leghorn chicks and 64-day-old Muscovy ducks were not. No serum antibody to IBDC virus was detected in 95 wild sandhill cranes collected in Wisconsin or Indiana in 1976 and 1977. However, 9 of 11 captive cranes in the affected area at the ICF had antibody to this agent.