The coat protein (CP) genes and flanking regions of three alstroemeria-infecting cucumber mosaic virus isolates (CMV-ALS), denoted ALS-LBO, ALS-IPO, and ALS-NAK, were cloned and their nucleotide sequence determined and compared at both nucleic acid and deduced protein level with the published sequences of CMV RNA 3. The sequences of these isolates showed more than 95% nucleotide and peptide sequence homology to each other and to other members of subgroup II CMV. Strikingly, an additional sequence of 218 nt was found in the central region of the 3’-non-translated region (NTR) of RNA 3 of two out of three isolates. The additional sequence appeared to have arisen from RNAs 1 or 2. A subgroup-specific DIG-labeled probe has been developed from this additional sequence and applied to detect subgroup II CMV strains in dot blot hybridization and to differentiate the Alstroemeria isolates containing additional sequences in Northern blot hybridization.