Low-temperature experiments in the ‘dry’ ternary Cu-Bi-S system, conducted by using sulphidation methods down to 120°C produced a new metastable solid solution series Cu₁₀Bi₂S₁₃-Cu₅Bi₂S₈ at 178°C coexisting with CuS. This transformed slowly at 190–200°C to an assemblage of either CuS-(Cu,Bi)₈S₉ or CuS-Bi₂S₃ or both, depending on available sulphur. Sulphidation experiments on Cu₃BiS₃ similarly revealed a solid solution range for the phase (Cu,Bi)₈S₉ of up to Cu/Bi = 3/2 at 178–190°C, and a lower stability limit of 138°C Isothermal sections of the system were constructed at 200 and 300°C, based on the new information collected but excluding the metastable series.