['The addition of carbogen and nicotinamide (CON) to radiotherapy (RT) improves overall survival in invasive bladder cancer. We explored whether expression of the hypoxia marker hypoxia-inducible factor-1α (HIF-1α) alone or in combination with other markers predicted benefit from CON.', 'A retrospective study was carried out using material from patients with high-grade invasive bladder carcinoma enrolled in the BCON phase III trial of RT alone or with CON (RT+CON). HIF-1α expression was studied in 137 tumours using tissue microarrays and immunohistochemistry. Data were available from other studies for carbonic anhydrase IX and glucose transporter 1 protein and gene expression and tumour necrosis.', 'Patients with high HIF-1α expression had improved 5-year local relapse-free survival with RT+CON (47%) compared with RT alone (21%; hazard ratio (HR) 0.48, 95% CI 0.26-0.8, P=0.02), no benefit was seen with low HIF-1α expression (HR 0.81, 95% CI 0.43-1.50, P=0.5). Combinations of markers including necrosis also predicted benefit but did not improve on prediction using necrosis alone.'] Does expression of hypoxia-inducible factor-1α predict benefit from hypoxia modification in invasive bladder cancer?