The synthesis of a series of peptides spanning the entire sequence of the protein nerve growth factor (NGF) has been carried out using solid-phase peptide synthesis (SPPS). A twenty-two residue peptide sequence from the carboxyl-terminal region of NGF was found to inhibit the binding of native NGF to its known receptor, in a cell-free assay. This fragment may define an area in the native NGF molecule which is important for receptor interactions. The optimisation of this initial fragment found that the inhibitory effect was retained when the fragment was reduced to a fifteen residue, disulphide-linked peptide. Further attempts at optimising this smaller fragment have been carried out by substituting unnatural amino-acids into the sequence, as well as altering the conformation around the disulphide bond. Several of the smaller NGF peptides have been investigated by high-field nuclear magnetic resonance (N.M.R.). The complete assignment of several analogues of the fifteen residue, disulphide-linked peptide has been achieved. Analysis of the 'through-space' interactions indicated that these peptides adopt only random conformations in solution. As a prelude to a total NGF synthesis, the assembly of the well-characterised protein, hen egg white lysozyme (HL) has been attempted in order to test the current methods for approaching the synthesis of large, multi-cysteine peptides. Some evidence that the peptide chain was successfully assembled has been presented and the difficulties encountered in attempts to purify and fold the protein are discussed.