Wheat is one of the more important agricultural crops in the USA, and the major production areas may be subjected to potentially damaging concentrations of ozone (O3). Since no information was available regarding the O3 sensitivity of winter wheat cultivars grown in the Midwest, plants of three cultivars were field-grown in open-top chambers and exposed to O3 daily throughout the spring growing season to determine impact on grain yield. Also included was a non-chambered ambient air plot. Tests were conducted over a two year period and compared. The study was initiated to provide further biological response data suitable for evaluating ambient air quality standards and for use in the NCLAN economic assessment of the consequences of O3 exposure to crops. The specific objective was to establish the exposure-response relationships between yield of three important cultivars of soft red winter wheat grown in the Midwest and chronic exposures to a range of O3 concentrations. (Copyright (c) 1985 Pergamon Press Ltd.)