The nucleotide sequences of the SH gene and its F gene flanking region were determined over a range of 322 nucleotides for two live vaccines, two vaccine-associated isolates, six wild mumps viruses, and an attenuated mumps virus and compared to other sequences already published. Comparison revealed that the vaccine strains were clearly different from each other and the postvaccination isolates were different from the vaccines used. The viruses were assigned to three known cocirculating viral lineages. The attenuated mumps virus possesses nucleotide sequences identical to those of its progenitor strain.