We reviewed immunological relationships between paramyxoviruses and molecular evolution of paramyxoviruses. (1) paramyxoviruses are divided into two groups by the basis of the immunological relationship, i.e., parainfluenza type 1 virus group and type 2 virus group; (2) according to the NP and M proteins sequences, paramyxoviruses are divided into parainfluenza type 1 virus and type 2 virus groups; the former group is composed of HPIV-1, SV, HPIV-3 and BPIV-3, and the latter group consists of HPIV-2, SV41, SV5, MuV, HPIV-4A and HPIV-4B; and this grouping coincides with that by immunological relationships; (3) alignment of the P and V proteins of paramyxoviruses demonstrates that irregular gaps are present around the RNA-editing sites, suggesting that dynamic processes have been occurred during molecular evolution; (4) the NP proteins of the morbilliviruses are more related to the parainfluenza type 2 group, while the M proteins show closer-relationship with the parainfluenza type 1 group; (5) the parainfluenza type 2 group can be subdivided into two groups, i.e., mammal and avian types; (6) phylogentic trees for mononegaviruses are constructed.