In 152 patients with multiple myeloma who had been treated with cytostatic agents the prognostic value of seven staging systems was evaluated: Carbone et al (1967); Acute Leukemia Group B (ALGB) and Eastern Cooperative Oncology Group (ECOG) (Costa et al, 1973); Southeastern Cancer Study Group (SECSG) (1975); Durie & Salmon (1975); Alexanian et al (1975); Merlini et al (1980); British Medical Research Council (1980). The staging systems of the ALGB (Costa et al, 1973) and SECSG (1975), both dividing patients into 'good risk' and 'poor risk' groups, showed significantly different survival curves. Nevertheless, despite statistical significance the observed differences were rather small. In the systems of Carbone et al (1967), Merlini et al (1980), Alexanian et al (1975) and Durie & Salmon (1975) some of the differences in the survival curves were statistically significant while others were not. Our data best fitted into the British Medical Research Council (1980) staging system, the survival curves of all three stages showing significant differences, with median survival time dropping from 83 months in stage A to 52 months in stage B and 26 months in stage C. Nevertheless, none of those systems was clearly superior to single risk factors, especially creatinine and haemoglobin.