Electron probe microanalysis of oxygen in a range of binary and ternary oxides is described. Experimental data are presented for a range of electron accelerating voltages and for two different take-off angle instruments. The ratio of oxygen K emission from specimen and standard is found to reach a limiting value, the same for each instrument, as the applied voltage is increased. The observations are shown to support the thin-film model (Duncumb and Melford 1966) proposed for quantitative analysis of light elements and also to enable its range of applicability to be established in terms of specimen characteristics and experimental conditions. The model is used together with chemical composition data for the oxides, and a consistent set of mass absorption coefficients are calculated which are considered to be accurate within 10%. These new data are discussed and compared with previously published values.