The concentrations of the HO2-RO2 species measured during July 11, 1990, in the ROSE (Rural Oxidants in the Southern Environment) study in Alabama are compared to those expected in theory from calculations based upon detailed hourly measurements of a variety of trace gases including the hydrocarbons, NO, NO2, carbonyl compounds, CO, PAN (peroxyacetylnitrate) and calculated jO3 values. The measurements are also compared with the [HO2] + [RO2] as estimated from deviations from the NO2 + hv (+O2) ⇄ NO + O3 photostationary state. Within the error of the measurements all of the data appear to be in reasonable accord.