The National Crop Loss Assessment Network (NCLAN) was formed in 1980 to assess the effects of air pollutants on major agricultural crop yields. NCLAN consisted of U. S. government and non-government organizations that conducted field experiments, crop yield modeling, and economic analyses. Ozone and sulfur dioxide were selected as the air pollutant treatments for NCLAN studies because they were known to cause damage to vegetation. Experimental methods and results from individual studies have been reported by the principal investigators in many publications. The purpose of the publication is to summarize the statistical methods used in the combined analyses, to present the polynomial and Weibull ozone dose-response equations determined in the combined analyses, and to summarize the effects of ozone on crop yields by presenting estimated relative yield losses for postulated levels of ozone pollution.