The introduction of Roundup Ready (glyphosate-resistant) and Liberty Link (glufosinate-resistant) corn hybrids has the potential to reduce the use of residual herbicides that may contaminate surface and groundwater and to provide control options for perennial weeds such as wirestem muhly in corn. The maximum environmental benefit of these weed control programs will only be recognized if it is known how much residual herbicide, if any, is required to make these programs dependable. In addition, the potential yield losses associated with total postemergence weed control programs must be understood if these programs are to be successful. Four experiments were conducted at several locations across NY state in 2000 to collect additional data concerning these issues.