Argyrophil nucleolar organiser regions (AgNORs) are increased in a variety of malignant cells compared with normal cells, and a recent study has claimed that AgNORs have prognostic value in colorectal cancer. We have studied the AgNOR counts in tumours from 95 colonic resections performed in 94 patients in whom a minimum 5 year follow-up was available. In 71 pathological specimens adjacent normal mucosa was also examined. There was a significant difference between AgNORs per cell in normal mucosa (median 1.46, range 1.10-1.80) compared with tumour cells (median 1.92, range 1.42-2.95, P less than 0.001). There were no significant differences in average AgNORs per cell between tumours in each Dukes' stage or category of differentiation. The average AgNORs per cell in tumours of patients surviving disease-free for 5 years was the same as that in tumours of patients dying of colonic cancer recurrence. We conclude that AgNORs have no prognostic value in colorectal cancer and are not correlated with Dukes' staging or differentiation of the tumour.