The NASA Goddard Space Flight Center/Wallops Flight Facility nitric oxide detector used in the July 1983 GTE/CITE 1 instrument intercomparison is a chemiluminescence system which, at that time, had a detection limit of about 2 pptv (S/N=1) for 60-s integrations. A substantial amount of NO concentration data was taken with this system at Wallops Island, Virginia, a site that should be typical of numerous nonurban coastal areas of the eastern United States and for which little other data are available. Midday concentrations under conditions of northwest winds averaged about 200 pptv, a value low enough to imply lower NOx amounts than are generally thought to exist in the eastern United States. During a 2-day period when the sampled air had spent 1--2 days over the Atlantic Ocean, average NO concentrations of 70 and 33 pptv were observed. Measurements at night indicated an average NO concentration of 16 pptv under wind conditions making contamination of the sampled air by local anthropogenic sources unlikely.