Abstract Project SAPPHO consists of a comparative analysis of ‘paired’ successful and unsuccessful technological innovations, where one half of the pair is a commercial success and the other a commercial failure. In phase I of the project twenty-nine pairs were investigated, seventeen in chemical processes and twelve in scientific instruments. Five main areas of difference between successful and unsuccessful innovators emerged which related to the innovator's understanding of user needs, efficiency of development, characteristics of managers, efficiency of communications and marketing and sales efforts. In phase II, the project has been extended to include a new total of forty-three pairs, twenty-two in chemical processes and twenty-one in scientific instruments. The results of phase I have been confirmed with the same five underlying factors emerging as strongly differentiating between success and failure and with some inter-industry differences becoming clearer. These differences, by and large, relate to the basic structural and environmental differences which exist between the two industries. Following the statistical analysis a subjective review was made of thirty-four failure cases, and those factors which contributed maximally to the individual failures were identified. The results of this exercise support the results of the statistical analysis, but they also highlight some new and significant factors. Finally, some of the more important of the many hypotheses which have been forwarded as offering explanations for innovative success were tested in the tight of the phase II SAPPHO results.