If activation of the p53 gene is involved in the progression or metastasis of colon cancer, it may affect the angiogenic phenotype in vivo. To verify this hypothesis, we studied the correlation between p53 accumulation and expression of thrombospondin-1 (TSP1) in colon cancer specimens. Levels of TSP1 gene expression were estimated by Northern blotting in 65 colon cancers. Accumulation of p53 and the distribution of TSP1 protein were evaluated immunohistochemically. Various levels of TSP1 gene expression were seen in colon cancers, while p53 accumulation was confirmed in 42 of the 65 colon cancers. The level of TSP1 gene expression demonstrated a significant inverse correlation with p53 accumulation in colon cancer. Colon cancer cells expressed TSP1 protein and p53 accumulation reciprocally in the same nests. These results suggest that alterations in the tumour suppressor gene p53 may inhibit TSP1 expression in colon cancer.