Three basic approaches towards the measurement of the visual quality of VDUs exist. These coincide with taking measures at the subject, description through display statistics, and obtaining user judgements. It is argued that the last has some specific advantages. Therefore a rating scale has been constructed for the measurement of the visual quality of alphanumeric displays. This Display Evaluation Scale (DES) is based on the notion that display quality is a multidimensional concept. The scale is intended for application in quite unrestrictive settings. The DES can be used as a design, evaluation or research tool. The DES, its development and software implementation are described. In the discussion of a number of experiments it is shown that a high reliability of the measurements can be achieved with a relatively small sample size. Preliminary results on the validity of the scale are presented briefly and implications for future research are indicated.