Our analysis focussed on 2 sets of NO2/NO ratios derived from the data; these were based on overlapping NO and NO2measurements made by 2 independent techniques; ie a chemiluminescent technique and a technique based on two-photon, laser-induced-fluorescence. While for any given 6-10min time interval the 2 observed NO2/NO ratios often exhibited significant discrepancies, these discrepancies appeared to be mostly random rather than systematic, and as a result, the average difference for all time intervals with overlapping NOxmeasurements was only 12%. The ratios predicted from photochemical model calculations were found to be reasonably consistent with the observed ratios, although on average they tended to fall about 20-25% below the observations. -from Authors