||This paper explores the use of patent statistics in identifying four aspects of technological structure, namely, the potential knowledge pool, cumulativeness, inter-firm homogeneity in technology levels, and the scope of innovations. The firms studied are sampled from the chemical (CHEM), the computer (COM) and the electrical and electronic (EE) industries worldwide. We find that the contributions of intra-industry spillover are low at 12%, 10%, and 9% for the three industries respectively. In addition, they can internalize 15%, 19% and 13% of their previous research efforts respectively. Fundamental innovations are relatively more important to the development of CHEM and less so for the other two industries. Lastly, we show that the results of empirical tests lend support to our specifications of these proxies.