The techniques of chromatography on poly (U)-cellulose and sedimentation and electrophoresis analysis were used to study poly(A)-containing virus-specific RNA of Newcastle disease virus. The poly(A)-containing molecules were shown to be present in approximately similar amounts (60-80%) in 18S, 24S, and 35S RNA. No poly(A)-containing molecules capable of interaction with poly(U) sepharose were found in 50S RNA. In 18S RNA there are 6 individual poly(A)-containing RNA-transcripts with molecular weights well correlating with those of virus proteins. The average size of poly(A) for 18S and 24S RNA is 60-70 nucleotide residues. In the sedimentation analysis of poly; A)-containing 24S and 35S RNA eluted from poly(U)-columns, some of the material sedimented in the zone of 18S RNA. The presence of complexes of two or several molecules with the sedimentation coefficient 18S in these RNA's is suggested.