The geological setting and chemistry of mineral springs and saline lakes in and near to the Western Rift Valley in Uganda are described. Most of them are neutral or alkaline in pH and have the anions chloride, sulphate and (carbonate + bicarbonate) present in concentrations of approximately equal magnitude. The composition of the brine and evaporite deposits at Lake Katwe suggest that the salinity of this and the other saline lakes is derived mainly by evaporative concentration of mineral spring waters. Hypotheses for the origin of the mineral spring waters are discussed and apparently they derive most of their solutes from a juvenile source although much of the water may be meteoric. Mineral waters from other parts of East Africa also have relatively high pHs and carbonate contents, but show regional chemical variations, notably in sulphate and fluoride contents. Such variations are considered to be genetic and to reflect regional differences in the Neogene volcanic rock suites.