In a preliminary study of two new analytical techniques, we have measured hydrogen peroxide (H2O2) and nitric acid (HNO3) near ground level at a rural site near Boulder, Colorado during February, 1978. H2O2 was measured with a liquid-phase chemiluminescence technique. HNO3 in a sample air stream was converted to NO2 in a packed quartz tube at 350 ¿C, and detected with a fast response NOx monitor. O3, CO, NO, and NO2 were also measured simultaneously. H2O2 was found between 0.3 and 3 ppb. HNO3 concentrations as high as 5 ppb were found with NOx always greater than HNO3 by at least a factor of 5.