The phylogenetic relationship among the salmonid fishes of the genus Oncorhynchus has been analyzed using various kinds of markers for a long time. However, there are three major disagreements among those studies; (1) the authenticity of the Pacific salmon group as a monophyletic cluster, (2) the phylogenetic relationship among three Pacific salmons (pink salmon, sockeye salmon, and chum salmon), and (3) the phylogenetic position of masu salmon. We used allozyme electrophoresis to clarify the phylogenetic relationship between the Pacific salmon group and the Pacific trout group. Furthermore, we reanalysed published mitochondrial DNA D-loop sequences (Shedlock et al., 1992). Allozymic data and mtDNA data indicated the following consistent results; (1) all Pacific salmons formed a monophyletic cluster, (2) chum salmon and pink salmon were clustered within those Pacific salmons, (3) masu salmon formed a cluster with other Pacific salmons and diverged first in this group.