There is currently some debate about which TQM practices contribute most to superior performance outcomes. Several proponents argue that softer TQM practices such as leadership, human resource management, and customer focus have more impact than benchmarking, process analysis or performance measurement. The evidence for which TQM factors contribute most to improved performance is not yet conclusive, and sometimes contradictory. Using data from a longitudinal study of 67 TQM firms we contribute to this debate. Our central hypothesis is that measurement of key TQM practices and performance outcomes is essential for TQM success. We examine the measurement practices of this cohort of firms, and report on the changes in their measurement behavior over time. Specifically, we analyze seven dimensions of measurement relating to customer satisfaction, employee satisfaction, process performance, impact of TQM on costs, impact of TQM on sales, self-assessment, and benchmarking. We calculate a measurement-intensity score for each firm, based on how many of these seven parameters were being measured, and we show that increased measurement intensity is strongly associated with perceived TQM success. Finally, using multivariate discriminant analysis, we identify eight variables that explain the level of TQM success with a classification accuracy of almost 90%. We conclude that to attain the highest levels of TQM success, firms need to engage in the measurement practices of self-assessment and benchmarking, but our data suggest that an appropriate measurement framework needs to be in place beforehand.