Research was conducted concurrently on basic experimentation into human individual differences in the night seeing process and on the development of instruments to test night seeing ability. Experimental testing revealed two major factors to be involved: (1) brightness contrast sensitivity and (2) visual acuity detail. A useful relationship was also determined between seeing ability at intermediate (moonlight) levels of illumination and at very low (starlight or moonless) levels. Development of instrumentation for night vision testing resulted in the engineering of the ANST-II, a compact, portable, rugged, and easy to use model. Field use, under varying conditions, demonstrated its practicability usefulness, and reliability in meeting Army night seeing testing needs. An ANST-II prototype has been made available to USCONARC for possible use in meeting various requirements for identifying soldiers possessing night vision ability. (Author).