The coordination chemistry of copper (I) covers huge fields, as shown by a survey covering the crystallographic and structural data of over one thousand examples. About 6.5 percent of those complexes exist as distortion isomers and are summarised. These are discussed in terms of the coordination about the copper (I) atom, and correlations are drawn between donor atoms, bond length and interbond angles. Distortion isomers, differing only by degree of distortion in Cu-L and L – Cu – L angles. Interestingly, that while in the copper(II) complex chemistry are several types of isomerism (distortion, cis-trans, linkage, coordination number a polymerisation), in the copper(I) complex chemistry only distortion isomerism has been found.