It is generally recognized that spring rainfall can result in losses of fertilizer nitrogen (N) from soils, but there is little agreement concerning the importance of these losses. Surveys of nitrate concentrations in Iowa cornfields over the past decade provide new information on this matter. The surveys were conducted as part of the N-Check Program, in which the late-spring test for soil nitrate and the end-of-season test for cornstalk nitrate were used to assess N-sufficiency levels in fields managed by producers.