ABSTRACT FIELD measurements of the overwinter soil moisture changes, those occurring from freeze-up up to the time of snowmelt, in the Canadian Prairies show that moisture losses are common from the shallow depth adjacent to the soil surface whereas, depending on the soil moisture content at the time of freezing, the amount of moisture in a 0 to 1 m soil layer remains unchanged or increases. It is shown that on irrigated areas the amount of moisture migration to a freezing front in the depth, 0 to 1 m, greatly exceeds snowmelt infiltration; in dryland areas overwinter changes represent, on the average, 20 to 50% of the soil moisture increase between fall and the end of snowmelt. The need for identifying the primary mode of transfer, liquid or vapor, is emphasized. Information is provided on the interrelationships between overwinter changes, fall soil moisture and soil temperature