Cotton grown in smogfree carbon filtered air produced 20 to 30% more raw cotton compared with similar cotton growing in non-filtered air at Parlier, Hanford and Cotton Center. At Five Points, on the west side of the valley, the difference in favor of filtered air was about 10%. Vegetative growth was apparently not influenced by the presence or absence of the oxidants removed by carbon filters, but senescence was delayed several weeks in the fall by the removal of existing pollutants. All these experiments were conducted with Acala SJ-1 cotton. Future experiments will be conducted with newly released SJ-2 and T-1307 and soon-to-be-released T-4852, to determine their relative tolerance to air pollution as compared with SJ-1. Breeding for smog resistance seems to be the most practical means of living with this problem, which from all indications to date, is serious in rnanv parts of the San Joaquin Valley.