In this paper we investigate the evolution of technological capabilities of Korean semiconductor firms. First, we focus on the notion of rate and direction of technological building based upon technological using and generating capabilities. The rate was measured by development time gap and technological activities, such as patenting and number of publications. In the second part we identify three aspects of directions of the technological building process using patent content analysis, specific technological characteristics of semiconductor technologies and product portfolios. We argue that Korean semiconductor firms have deepened their technological capabilities and the measurement of this process is a key contribution of this paper. (C) 2000 Elsevier Science Ltd. All rights reserved.