Taxonomic and phylogenetic studies of firefly in Japan have been reviewed. Fourty-six lampyrid species and one rhagophthalmid are distributed in the Japanese Islands including the Ryukyus. Recently, molecular phylogenetic approaches have been employed in the systematic study of firefly using mitochondrial and luciferase genes. Based on the molecular phylogenetic trees, evolutionary process of flashing patterns related strictly to mating behavior was estimated. Furthermore, genetic diversity studies revealed geographic differentiation patterns within species, and conservation measures of firefly were proposed to protect genetic resources endemic to the localities.