The Night Operations Program is concerned with optimizing human performance in relation to night vision devices and related sensors. Specific aspects deal with determining performance effectiveness of sensor systems, factors which affect performance, and means of improving effectiveness. The present study describes research involving the use of such devices in assessing the effectiveness of soldier performance during night operations. The primary objective of the experiment was to investigate the effects of search area size on performance--as it interacts with a number of environmental, target, and human factors--and to determine the implications of findings for operational use, basis of issue; and search deployment, as well as for improvement of soldiers' effectiveness in using these devices.