This paper describes the field performance of the Kodak EKTACHEM GLU/BUN Analyzer for glucose and urea. NCCLS protocols PSEP-2, 3 an 4 were used which enable manufacturers to establish performance claims concerning the precision and accuracy of an analytical system. This multicentre trial used four analysers in four European countries, United Kingdom, France, West Germany and Italy to assess within and between laboratory performances. Freeze dried control materials were used for the performance check experiment PSEP-2 and for the replication experiment PSEP-3. The replication study, although very time consuming, was straight forward to undertake and the results were comparable between centres. Compliance with the protocol for comparison of methods experiment PSEP-4 in which laboratories used their own hospital patient samples was more difficult. The problems with obtaining suitable samples and the performance of comparative methods are discussed in detail.