Changes in the moisture content of summer fallowed soil in tanks 15 in. in diameter and 5 ft. deep set in pits in the centre of field plots at the Dominion Experimental Station, Swift Current, Saskatchewan, which have been recorded at fairly frequent intervals during the summer months since 1922, provided two series of data, comprising observations in May and June and those in July and August. These have been analysed statistically in order to relate conservation to precipitation after making allowance for other variable factors. Five-factor regression equations, fitted by the method of Least Squares, gave multiple correlation coefficients of 0.95 and 0.96 between the computed and observed conservation in the two series. It is inferred from these equations that under average conditions a one-day rain to the amount of 0.36 in. in May-June and 0.46 in. in July-August would be required just to offset the subsequent evaporation during a 10-day period. Increased penetration and retention of the heavier rainfalls is very definitely indicated, and it is calculated that whereas on the average 66% of a one-day rain of 1 in. in May-June would still be conserved at the end of 10 days, only 30% would be retained if the same amount was received in five daily showers each of 0.20 in. The intensity as well as the total amount of precipitation is thus emphasized as a factor of prime importance in its relation to soil moisture under semi-arid conditions.