San Joaquin cotton production records show outstanding progress during the past decade. Lint yield in this one-variety district averaged 625 pounds per acre for the first three years of the decade (1951-53) compared with 1020 pounds for the last three years (1958-60). This gain of 63 per cent in yield is attributed to a combination of (a) varietal improvements in Acala 4-42, and (b) the better “know-how” employed by the grower. Textile mills have recognized improvements in spinning quality to the extent that the demand for California's Acala 4-42 far exceeds the supply.