Syndecan-1 is a ubiquitous and multifunctional extracellular matrix proteoglycan,which mediates basic fibroblast growth factor (bFGF) binding and activity. Shedding of syndecan-1 ectodomain from the plasma membrane is highly regulated. We evaluated the influence of soluble syndecan-1 and serum bFGF determined by ELISA on outcome in 184 lung cancer patients (non-small cell lung cancer, n = 138; small cell lung cancer, n = 46). Serum syndecan-1 and bFGF levels were determined from sera taken before treatment. The median follow-up of the patients alive (n = 21) was 8.1 years (range, 6.6-8.9 years). High serum syndecan-1 and bFGF levels tended to occur in the same patients (P = 0.044). When the serum values corresponding to the highest tertile were used as the cutoff value, the median survival time of the patients with a high serum syndecan-1 level (>59 ng/ml) was 4 months [95% confidence interval (CI), 3-6 months] as compared with 11 months (9-16 months) among those with lower serum levels (P = 0.0001), and the median survival time of the patients with a high bFGF level (>3.4 pg/ml) was 5 months (3-8 months) versus 11 months (8-14 months) in those with a lower level (P = 0.023). In general, the prognostic influence of both factors was independent of the histological subtype. Both serum syndecan-1 level (relative risk, 1.8; 95% CI, 1.1-3.1) and serum bFGF level (relative risk, 1.6; 95% CI, 1.0-2.7) had independent influence on survival in a multivariate survival analysis in non-small cell lung cancer. We conclude that high serum syndecan-1 and bFGF levels at diagnosis are associated with poor outcome in lung cancer.