We studied the growth characteristics and hypoxic fractions of DLD-2 human colon tumours xenografted into male nude mice either in the unperturbed state or after i.p. injection (q.i.d. x 7) of basic fibroblast growth factor (0.25 mg kg-1) or suramin (50 mg kg-1). This evidence concerns the gene FGF2 and colonic neoplasm.