The inheritance of colour in horses had been investigated for many years but since Adalsteinsson's findings on basic and diluted colours, made in the seventies, opinions have changed considerably. Many authors supported this hypothesis by detailed breeding and laboratory experiences. This article contains a review of the most important publications concerning the mode of inheritance of all known horse colours. Some of the papers were published long ago but are still valid. The role of different loci determining horse colour is discussed in relation to other mammals and to the current knowledge on melanogenesis. The paper presents references for 14 loci responsible for horse coat colour.