This article describes the activities of the EORTC Health Economics Unit since its inception in early 1994. The aim of the unit is to carry out economic evaluations of competing treatment options in common cancers in order to provide health care decision makers with useful information about the relative benefits and costs of the therapies they have to choose between. These assessments are mainly carried out by integrating collection of economic data in selected phase III randomized controlled clinical trials conducted by the EORTC collaborative groups. Studies with an economic evaluation integrated are currently becoming mature enough for analysis and several publications have resulted or are in press. Some studies with data from other sources than EORTC trials have also been performed and published. In addition, the unit has actively followed and contributed to the continuous methodological development in the field of economic evaluation of health care interventions.