AbstractThe prognostic significance of nucleolar organizer regions (NORs) in renal cell carcinoma (RCC) was evaluated. NORs were quantified in a series of 182 cases of RCC using the silver‐colloid method. The cases were staged according to Robson's method (48 stage I, 26 stage II, 33 stage III, 75 stage IV) and mean NOR numbers for each tumour were correlated with survival over a 5‐year period. Localized tumours (stages I and II) with low NOR numbers had an almost 100 per cent 5‐year survival. Those patients with clinical evidence of metastases at presentation showed a high mortality, although those with low numbers of NORs had a significantly increased disease‐free interval. Statistical analysis using the log rank test indicated NORs to be a significant predictor of survival over the whole series (P= 0·0001) and within each of Robson's stages (P= 0·0008 stage I,P= 0·0154 stage II,P= 0·0009 stage III,P= 0·0001 stage IV). Analysis of data using Cox's proportional hazard model showed mean NOR numbers to be independent of stage as a predictor