Heparin and heparan sulphate (HS) are heterogenous, linear, polysulphated polysaccharides that are important in the regulation of a wide variety of biological processes including blood coagulation, in cell differentiation, adhesion, invasion, migration and development, and in tumor-related cellular events such as growth regulation and metastasis. In general, heparin/HS interacts with proteins mainly through ionic interactions between its negatively charged groups and positively charged groups on the proteins. From a mechanistic or therapeutic standpoint, it is attractive to design less complex charged molecules, other than oligosaccharides, as mimics of heparin. In an attempt to improve the accessibility of heparin mimics, it was assumed, provided that the correct charge topography could be achieved, that sulphated peptides might also act as mimics. Therefore, sulphated peptide combinatorial libraries were generated on solid support to identify novel polyanionic structures that mimic the role of heparin/HS in its binding to fibroblast growth factors (FGFs). Libraries were synthesised by direct sulphation of the peptide on solid phase or by using O-sulphonated building blocks during peptide synthesis. Quantitative solid-phase O-sulphonation of hydroxy amino acid residues in a peptide chain was effected by sulphur trioxide pyridine (SO₃-Pyr) complex in anhydrous pyridine at 65°C for 4 h. O-Sulphonated building blocks were successfully synthesised in solution and, after stabilisation of the sulphate group by complexion with tetrabutyl ammonium ions, were employed in the synthesis of sulphated peptide libraries, similar to those generated by direct O-sulphonation on solid supports. The libraries were incubated with fluorescent-labelled FGF-1, and analysis and sequence determination of active compounds was carried out using Edman degradation. Selected sulphated peptides from the screening were resynthesised and their affinity for FGF-1 (acidic FGF) was studied in solution competition assays using surface plasmon resonance. These studies showed that sulphated decapeptides do bind to FGF-1 and inhibit its binding to immobilised heparin in the low micromolar concentration range.