Abstract: A hand-held circular saw which is characterized by a gasoline-powered, trigger-operated blade drive unit connected to a conventional circular saw by means of a specially-designed adaptor. In a preferred embodiment the circular saw is characterized by a circular saw blade rotatably mounted in a saw housing which is connected to a drive shaft housing and adjacent gear housing. The adaptor is secured inside the drive shaft housing, and the blade drive shaft extends from connection to a blade-driving gear train inside the gear housing, and through the adaptor and projects from the drive shaft housing. The blade drive unit receives the protruding blade drive shaft, and is fitted with an attachment collar which removably receives the adaptor to connect the blade drive unit to the circular saw. The gasoline-powered circular saw is lightweight, efficient and suitable for outdoor home, farm or commercial use.