Pancreatic cancer is a malignant tumor with an extremely poor prognosis. Thrombospondin-1 (TSP-1) was suggested to be a potential regulator of tumor growth and metastasis. We examined TSP-1 expression in 77 cases of invasive ductal adenocarcinoma of the pancreas, and analyzed the correlation between the TSP-1 expression pattern and clinicopathological features in pancreatic cancer. TSP-1 immunoreactivity was detected in the cancer stroma. The diffusely positive and focally positive patterns of TSP-1 were found in 33 (42.9%) and 40 (51.9%) of 77 cases, respectively. The TSP-1 diffuse expression was significantly correlated with lymph node metastasis (p<0.01), neural invasion (p<0.05) and TNM stage (p<0.01). The prognostic significance of clinicopathological parameters were analyzed by univariate and multivariate analysis using the log-rank test and the Cox proportional hazards model. Based on the univariate analysis, histological differentiation (p<0.01), lymphatic invasion (p<0.01), venous invasion (p<0.05), neural invasion (p<0.01), TNM stage (p<0.01) and TSP-1 expression (p<0.01) were significant parameters. These observations suggested that TSP-1 plays important roles in cancer cell growth and metastasis of human pancreatic cancer, and that stromal TSP-1 immunoreactivity is a good prognostic predictor of patients with pancreatic cancer.