To compare the Charing Cross Hospital scoring system with FIGO staging for gestational trophoblastic disease. A retrospective analysis of patients referred to Charing Cross during the period 1979-1989. National referral centre. Two hundred and seven women with gestational trophoblastic disease presenting between 1979-1989. The women were classified according to the Charing Cross Hospital scoring system and FIGO clinical staging and the results of treatment compared. Of the 207 women studied, there were 102 low risk, 39 medium risk and 66 high risk according to the Charing Cross system and 26 stage 0, 83 stage 1, 23 stage 2, 51 stage 3 and 24 stage 4 according to the FIGO system. If the FIGO system had been used to determine therapy, 17 women would have been at risk of undertreatment and nine of overtreatment. The main prognostic factors contributing to a higher Charing Cross score and thus more intensive chemotherapy from the outset were: HCG > 10(5), interval from antecedent pregnancy > 12 months and term delivery. The Charing Cross scoring system incorporates factors predictive of the presence of drug resistant tumour and thus allows more appropriate use of chemotherapy from the start of treatment than is possible with the anatomically based FIGO staging. Moreover, the system is easy to apply relying only on history and clinical examination in addition to a reliable quantitative HCG assay.