A single pass herbicide program has become the goal of many corn producers throughout the state. The apparent time and cost savings in controlling weeds with a single pre or post-emergence herbicide application is the driving force behind this trend. While there are situations where a single pass strategy will work, it has weaknesses that can result in inconsistent performance. Some single pass pre-emergence programs sacrifice control of large seeded broadleaves and perennials, and many are strongly influenced by the timing of rainfall. New chemistries, increasing no-till acreage and increased use of herbicide resistant crops have resulted in a number of single pass postemergence herbicide programs. Although this provides the opportunity to scout and select herbicide programs to best match weed spectrum, timing is critical for effective control. Since most fields contain several problem weed species, timing a single application to effectively control all species can be difficult.