The invention relates to methods for the stabilisation of cytokines and to cytokines generated by such methods. The methods of the invention involve mutating the amino acid sequence of a cytokine so as to remove solvent-exposed hydrophobic residues, and/or mutating the amino acid sequence of the cytokine so as to stabilise one or more secondary structure elements in the molecule. These steps have the effect of destabilsing intermediates that are formed during the folding process, relative to the stability of the cytokine in its naturally folded state, so increasing the yield of the cytokine as produced in vitro.