The chemistry of the rare sulphosalt nuffieldite from three localities in Slovakia is examined.Nuffieldite is a part of a complex association of Bi sulphosalts accompanying tetrahedrite mineralization insome sulphide deposits in the Western Carpathians. Cu + Pb = (Bi,Sb) + vac. substitution in nuffielditeand the general formula Cu1+xPb2Bi2(PbxSbyBi1–x–y)S7where 0 < x < 0.34; and 0.32 < y < 0.45 are confirmed.Decreasing Sb content with increasing copper content indicates a predominant substitution of Bi by Sbin nuffieldite.