To improve the efficiency and effectiveness of clinical laboratories, workflow analysis should be applied. To achieve this, specific laboratory functions and processes were identified. Methods for analyzing workflows and rules to control them are discussed. It is shown how workflow analysis can be applied in clinical laboratories using discrete event simulation. For this, a particular model (scales: support and consequences through advanced laboratory expert systems) is applied to analyze the workflow on several workstations. The results of a validation attempt are given. The information obtained from this study appeared to be very useful both from a methodological as well as a practical point of view.