Many kinds of molecular markers are now available in research and monitoring forest pests. Protocols required for analyzing insect protein and DNA are described, and the literature on molecular markers for five common pests in temperate forests are reviewed in this article. Techniques of molecular ecological methods : sequencing, PCR-RFLP, SSCP, microsatellite, SNPs, RAPD, AFLP and allozyme are explained. Thereafter, case studies of Lymantria dispar, Ips typographus, Thaumetopea pityocampa, Tomicus piniperda, Semanotus japonicus where molecular information was used to study forest insect populations are presented. They show that insect evolutionary history and migration can be elucidated through analysis of genetic population structure. Analyses of intraspecific and interspecific genetic differentiations can be applied to identifying species that are difficult to recognize using morphological traits. For facility of adopting the molecular techniques, I also argue the suitable methods to preserve specimens for DNA and protein experiments.