Abstract: Analyses which have been made in the past have shown no significant trend in annual values of rainfall during the period of rainfall records in the southwestern United States. In the present study, frequency of daily rains of various sizes are analyzed for four long-record stations in New Mexico. Frequency of rains of various sizes comprising wet years and dry are compared. Some effects of changes in rainfall frequency on vegetation and erosion are discussed. Originally published: Transactions of the American Geophysical Union; v. 32, no. 3 (June 1951).