Summary This paper uses United States patent classification analysis to study the development of core technologies and key industries in Taiwan over the last 25 years, from 1978 to 2002. After counting the number of Taiwan-held United States granted utility patents, the authors divide the years into three phases: from 1978 to 1994, with less than 500 patents each year; from 1995 to 1999, with 500-2,500 patents each year; from 2000 to 2002, with annual patents greater than 2,500. The results show that for both Taiwan’s core technologies and key industries, there was a great diversity at the first phase, while a mainstream forms and matures at the second and the third phases. However, industrial development at the third phase was more concentrated and focused than previous ones. Overall, Taiwan has clearly moved from a manufacturing-based economy to an innovation-based one, with its focus on high-tech industries during the previous 25 years.