Continuous quality assurance (QA) in health care has necessitated the adoption of statistical methods developed as industrial process monitoring techniques. One such statistical technique is the cumulative summation (Cusum) methodology, which can monitor continuously a production process and detect subtle deviations from a preset defined level of achievement. The method is practical, simple to apply, easy to introduce and has proved popular with trainees in some specialities. This article introduces the concepts of a sequential analysis, deals with the practical steps of setting up a data collection and monitoring performance for procedures in health care.