A variant of human interferon‐gamma (IFN‐γ) has been created in which the two chains of the homodimeric cytokine were linked N‐ to C‐terminus by an eight residue polypeptide linker. The sequence of this linker was derived from a loop in bira bifunctional protein, and was determined from a structural database search. This “single‐chain” variant was used to create an IFN‐γ molecule that binds only a single copy of the α‐chain receptor, rather than the 2 α‐chain receptor: 1 IFN‐γ binding stoichiometry observed for the native hormone. Crystals have been grown of a 1:1 complex between this single‐chain molecule and the extracellular domain of its α‐chain receptor. These crystals diffract beyond 2.0 Å, significantly better than the 2.9 Å observed for the native 2:1 complex. Density calculations suggest these crystals contain two complexes in the asymmetric unit; a self‐rotation function confirms this conclusion.