A summary of the development and impact of the Night Vision and Electronic Sensors Directorate (NVESD) Time-Limited Search (TLS) Model for target detection is presented. This model was developed to better represent the search behavior when an observer is placed under time-constrained conditions. The three primary components of the search process methodology are (1) the average detection time (based on characteristics of the image), (2) occurrence and time delay associated with false alarms, and (3) the time spent searching a Field-of-View (FOV) before moving on to another FOV. The results of four independent perception experiments served as the basis for this methodology. The experiments, which were conducted by NVESD, portrayed time limited search conditions for different sensor resolution and background clutter levels. The results of the experiments showed that these factors influence the search process and their impacts are represented within the components of the TLS methodology. The discussion presents the problems with the current model and details the constraints that must be understood to correctly apply the new model.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.