This dissertation reports findings from two laboratory experiments and a field study demonstrating significant reliance by users on interface layout information in interactive tasks. In Experiment l, a paradigm was introduced where either the layout of the interface was changed or labels were removed, after participants completed a minimum of eleven trials of a routine computer-based task. Since layout change had a more detrimental effect on performance, in Experiment 2, two methods expected to mediate that effect were explored: the addition of color and a layout based on a simple preexisting rule of top-to-bottom control order. Only the latter was effective, showing that introducing an interface layout that leverages preexisting knowledge can actually improve task performance. In the field study, a methodology was developed to put these findings to the test at a local family medicine clinic using an electronic medical records system. By studying nurses' use of an existing data entry form, a new form was designed to more closely follow their workflow. Similar to the top-to-bottom control order manipulation in Experiment 2, the new form layout seemed to produce better performance and was liked better by the nurses. Thus, in contrast to the vast body of literature in the field that has emphasized the importance of label information (e.g., Polson & Lewis, 1990) and goal structure (e.g., John & Kieras, 1996) in computer-based tasks, these findings reveal that users quickly learn to rely on layout information.