The absorption cross sections of ozone have been measured in the wavelength range 185-350 nm and in the temperature range 225-298 K. The absolute ozone concentrations were established by measuring the pressure of pure gaseous samples in the 0.08- to 300-torr range, and the UV spectra were recorded under conditions where less than 1% of the sample decomposed. The temperature dependence is significant for wavelengths longer than ~280 nm. The absorption cross-section values around 210 nm were found to be about 10% larger than the previously accepted values.