Chloride fertilization has consistently increased winter wheat grain yield and mature kernel weights at sites with physiological leaf spot (Table 1). Yield responses to applied Cl averaged 6.9 bu/a or 10.0 %, but can vary considerably with location. Thousand kernel weight increases from applied Cl averaged 7.2%, hence kernel size is the most important yield component affected by Cl. Leaf spot suppression by Cl may explain a portion of the yield responses. A reduction in photosynthetic area due to lesion formation, particularly in the flag leaves, could affect yield by reducing kernel size at harvest.   Physiologic leaf spot is a problem of low Cl testing soils. The solution to correcting potential damage from physiologic leaf spot is to increase soil Cl, through fertilization, to levels above the threshold damage level. In the absence of soil testing (many soil testing labs currently do not perform soil Cl tests) it is recommended that growers apply 20-25 lbs/a Cl (40-50 lbs/acre 0-0-60 material) to fields where physiologic leaf spot has been a problem. Granular 0-0-60 is the most economic source of Cl to apply (.17/lb Cl), and the material application cost of this recommendation is only $3.40 to $4.25/acre. This material can be blended with nitrogen, and broadcast applied in the fall, or early spring to produce satisfactory results. While yield responses to Cl fertilizer at sites with physiologic leaf spot are variable, the cost of correcting physiologic leaf spot through 0-0-60 fertilization is small when contrasted with the potential for improved yields and economic return.