The expression of components of the plasminogen activator system was investigated in patients with oesophageal carcinoma. Tumour and normal mucosa were obtained from resected oesophageal carcinomas and antigens were measured by enzyme-linked immunosorbent assay. Median levels of urokinase plasminogen activator (uPA) and the uPA receptor were higher in carcinoma than in matched normal mucosa (squamous cell carcinoma: uPA 4.05 versus 0.66 ng antigen per mg protein, uPA receptor 1.95 versus 0.50 ng/mg, n = 10, P < 0.05; adenocarcinoma: uPA 2.16 versus 0.61 ng/mg, uPA receptor 2.01 versus 0.49 ng/mg, n = 8, P < 0.05). Tissue plasminogen activator (tPA) level was lower than control values in squamous cell carcinoma but not in adenocarcinoma (1.97 versus 4.70 ng/mg, P < 0.05). There was no difference in plasminogen activator inhibitor (PAI) 1 level between carcinoma and normal mucosa. The PAI-2 level was lower than that in normals in adenocarcinoma only (6.0 versus 64.77 ng/mg, P < 0.05). These data support the hypothesis that membrane-bound uPA has a role in the breakdown of extracellular matrix in invasive oesophageal carcinoma.