Experiments were conducted in 1989 and 1990 to evaluate the response of cotton (Gossypium hirsutum L. cv. Deltapine 50) to sulfur (S) applications on sandy soils and develop soil and plant diagnostic criterion to improve the accuracy of S fertilizer recommendations. Applied S increased cotton yield only in 1989. This response occurred on a deep sandy soil. Two foliar applications (magnesium sulfate) were required for maximum yield. Leaf blade and petiole S appeared to be good indicators of S deficiency. The sulfate-S content of petioles was well correlated with soil-applied S throughout much of the growing season in 1990.