An improved method for the determination of ferrous iron in soil is outlined and sources of possible error discussed. The ferrous-iron content of soils in the black and the gray wooded soil zones in Alberta was determined. The effect of soil moisture on the ferrous-iron content of the soil was studied. Expts. to elucidate the properties of soil ferrous iron showed: Well-drained, healthy soils investigated, contained very small quantities of ferrous iron. In some samples the presence of the divalent iron was not detected. Under waterlogged conditions large quantities of ferrous iron were produced rapidly, after an initial lag of 2-3 days. This is mainly a biological process. The soil ferrous iron is not readily brought into soln. by water, but by the use of salts the ferrous iron can be displaced from the soil. NH4Cl proved to be the most efficacious for this purpose. This would indicate that ferrous iron enters into the base-exchange complex of soil. Under anaerobic conditions, soil water could dissolve quantities of ferrous iron, but much larger amts. of the divalent iron were held by the soil base-exchange complex. The Eh values indicate that the activity of the reducing agents present in waterlogged soil is greater than the reductive activity of ferrous iron. Ferrous iron in soil becomes readily oxidized if aeration of the soil is improved. Ferrous iron is formed when soil is steam-sterilized, and some of this divalent iron persists in the soil for a considerable length of time. Sunlight facilitates the reduction of iron in some soils and soil extracts. Iron may act as a catalyst, and sunlight as a source of energy in the oxidation processes in soils.