Data obtained during many years of continuous ozone monitoring at 12 selected EUROTRAC-TOR (Eureka environmental project: European experiment on Transport and transformation of environmentally relevant trace Constituents in the troposphere over Europe, subproject Tropospheric Ozone Research) network stations were analyzed by applying Fourier transformation (FT). FT averaged over the years, autocorrelation functions and FT of such functions were calculated for each site. As expected, strong frequency signals are found for the 1 year and 1 day periods. The relative intensity of the 1 day peak can be correlated with the intensity of local photochemical pollution as represented by a photochemical pollution index. A collective FT spectrum for seven European stations was calculated. This comparison confirms the existence of a common variation in ozone volume fractions with quasi-periods ranging between 7 and 44 days. These frequencies are most probably connected with quasi-cyclic synoptic scale meteorological influences. A comparison of meteorological data from the station Zugspitze showed similar periodicities.