Pine sawfiles are the insects, larval stage of which infest needles of pine especially Pinus kesiya cultivated on the mountains in the North. The studies took place in the cultivated areas and in the mixed forest areas in Chiang Mai during 1977-79, 1981-82. Five species of pine sawfiles were found : Nesodiprion biremis, Diprion hutacharernae, Gilpinia marshalli, G. leksawasdii and G. paitoon. Four pine sawflies’ species were investigated on external morphology, life history, two on infestation, all the five on population. Parasitoids, temperature, relative humidity and the amount of natural rainfall were also recorded.