The occurrence of areas in Manitoba where the productivity of soil is impaired by the presence of excessive amounts of soluble salts has been known since the time of the early settlers. The distribution and extent of these areas has been determined over most of the agricultural portion of the province through the operations of the Manitoba Soil Survey. The mapping of saline soils by this survey has been based on morphological features expressed in the soil profiles, such as pseudo-mycelium and crystalline gypsum, together with observations of native vegetation or crop growth. Investigations to determine the amount and composition of the soluble salts have been limited mainly to areas of special interest and to soil samples submitted to the Soils Laboratories of The University of Manitoba by farm operators. In order to gain a more comprehensive understanding of halomorphism in Manitoba soils, the investigations herein recorded were undertaken to ascertain the nature of the salts in different parts of the province and the concentrations at which they occur. Arising from these studies, some theories are advanced concerning the possible origin of these salts based on a consideration of their composition and of the geology of the areas.