A simple, standardised procedure was used for processing data from External Quality Assessment Schemes and for producing performance charts. A graphic presentation of cumulative performance is generated for each test, using an integrated software package to display results in a standardised format. This permits interpretation of satisfactory and poor performances and facilitates identification of "outlying" results. Although most results are recorded as Deviation Indices, the system is flexible and can be used to present other performance variables, such as Percentage Deviations and relevant textual information relating to interpretative assessments. It is therefore readily adaptable for use by other pathology disciplines.