About 70% of the molecules in the total RNA preparation isolated from barley stripe mosaic virus (BSMV, Norwich strain) were capped, i.e., contained a 5'-terminal inverted 7-methylguanosine. At least two individual components of the genomic RNA (RNA 1 and RNA 3) were capped. Thus the RNA components of BSMV contain both a 3'-poly(A) sequence (A. A. Agranovsky et al., Virology91, 95-105, 1978) and a 5'-terminal cap.