The authors respond to an article, Assessing Mild Traumatic Brain Injury, that appeared in the November/December 1998 issue of the Guides Newsletter . The authors of the article referred to several shortcomings of neuropsychological assessment; specifically, they questioned the ecological (real-world) validity of such testing for less severely impaired individuals. The authors of the letter agree that neuropsychological testing may underestimate problems with attention, concentration, and memory that patients experience in real-world settings. The letter writers identify research that indicates a correlation between neuropsychological test findings and an individual's ability to perform in a work environment, and they emphasize the need to consider the individual's environment before determining the degree of functional impairment based on neuropsychological test findings. The letter writers also suggest that evaluators use recently developed measures of malingering in test batteries, and they dispute the existence of an “overreliance on technicians for test administration.” The authors of the original article respond that questions of ecological validity are less relevant when neuropsychologists do not generalize from test scores to real-world performance. The authors of the article mention their work in detecting malingering and report only preliminary and variable success. Finally, the authors of the original article note that limited space precluded discussion of all the issues raised by the letter's authors.