This paper attempts to make a conceptual model of technological development in Korea based on the case studies concerning POSCO in steel industry and Samsung in semiconductor industry. Major findings are as follows. First, POSCO and Samsung made a large-scale investment continuously, and it worked as a source for rapid technological development. Second, two firms utilized overseas training for technological acquisition at initial entry point. Third, they extended technological domain from technology with low entry barrier to high level technology. Fourth, they joined main stream of technological development by timely choice of advanced technologies. Fifth, they accelerate the speed of technological development by establishing various forms of concurrent development system. Sixth, after the completion of technological catch-up, they pioneered new technological paths for the first time in the world. These characteristics of technological development in POSCO and Samsung can be applied to other scale-intensive firms in Korea.