The objective of this paper is to explore the extent to which a set of indicators of technological and industrial change can act as warning signals for technical change. A particular kind of technical change can give a new substitute such price/performance attributes that it is taken into the reach of mass market segments. Two processes of discontinuous technical change in the machine tool industry are analysed using patent data, bibliometrics, data on new entrants, relative price changes and diffusion data. In the first case (the transition from conventional to CNC machine tools) relative prices and new entrants were the first indicators to react whilst patents and bibliometrics increased in activity in parallel with the large scale diffusion of CNC machine tools. In the second case (the transition from CNC machine tools to flexible manufacturing systems) new entrants and publishing preceded the large scale diffusion by some years. The different patterns between the two cases and between these and what can be found in the literature, suggest that more work needs to be done to understand the conditions under which changes in each of the indicators can be used as a warning signal. The paper is concluded by a brief discussion which may form the basis for some further work in that direction.