In this paper we report on our empirical study of SPI programmes in thirteen UK software companies. We focus on companies’ approaches to SPI and how measurement relates to SPI in those companies. We present quantitative data characterising SPI and measurement in the companies. We discuss how the use of measurement relates to the maturity of software processes and how measurement supports maturing processes. Our results show that companies are generally enthusiastic about implementing measurement and they believe that SPI is impoverished without measurement. However our data shows that in reality companies have implemented very little substantive measurement. Indeed we suggest that companies find implementing measurement within SPI more difficult than they expect. Furthermore, we report on data from software personnel suggesting that companies are reluctant to implement measurement because it is difficult to justify in terms of quick pay backs. Overall our research suggests that despite companies knowing that measurement is fundamental to SPI, it is rarely implemented effectively.