Angiogenic cytokines in the plasma and serum of cancer patients may serve as 'surrogate' markers of tumour neoangiogenesis. Serum VEGF correlates with disease stage in colorectal cancer (CRC), but the role of bFGF in CRC is uncertain. This study aimed to assess plasma bFGF levels in CRC patients before treatment, during chemoradiotherapy and at one-year follow-up. Plasma samples were taken from 124 CRC patients, 26 polyp patients and 55 controls, and bFGF levels were measured by ELISA. 19 patients underwent pre-operative chemoradiotherapy. One-year follow-up samples were available from 48 disease-free patients and 18 patients with progressive disease. There were no detectable differences between plasma bFGF levels in polyp, Dukes' A or B patients (4.55, 5.77, 4.25 pg/ml, respectively), but there was a significant increase in metastatic CRC patients [Dukes' C and D (7.42 and 6.6 pg/ml; P = 0.004 and 0.048, respectively)], relative to median control levels of 4.14 pg/ml. At follow-up, there was a significant fall in plasma bFGF levels in disease-free patients (pre-op 6.09 and follow-up 3.45 pg/ml, P = 0.0004), but a non-significant rise in 18 patients with progressive disease (pre-treatment 5.90 and follow-up 9.99 pg/ml, P = 0.33). Pre-treatment plasma bFGF in patients receiving chemo-radiotherapy was similar in those with responsive and non-responsive tumours. There were no detectable changes in plasma bFGF through the adenoma-carcinoma sequence or patient groups with non-metastatic cancers. Elevated plasma bFGF was, however, associated with metastatic spread. The significant fall in bFGF in disease-free patients following therapy suggests that bFGF may be useful in clinical practice.