In December 1968 Varo, Inc. began predelivery evaluation of an airborne night vision system (NVS) that we developed for the U. S. Air Force. A major performance factor that had to be measured was the maximum range (RMAX,)at which the NVS operator could acquire a target on the terrain under varying conditions of darkness and background contrast. This paper describes the restraints encountered in measuring (RMAX.) and the approach that was finally derived for doing so with the required high precision. At this writing, NVS details including performance such as (RMAX.) remain DOD classified. Consequently, data provided herein do not include the dimensions of targets that were acquired. Therefore, the values that can be calculated from those data given should not be construed as absolute.