Economic statistics are often influenced by seasonal variations which impact on the activity being measured. The seasonal adjustment of economic statistics removes the seasonal component in the measured activity to render historically comparative observations for analysis. The seasonal adjustment process is expected to treat and eliminate patterns in an economic time series that are usually repeated annually and mask underlying movements in a time series. Seasonal adjustment should not be applied in instances where a time series does not display any recurring seasonal pattern. This article defines seasonality in economic statistics and presents the seasonal adjustment methodology applied by the Economic Statistics Department (ESD) of the South African Reserve Bank (SARB). All statistics published in the statistical tables section of the SARB’s Quarterly Bulletin which are seasonally adjusted by the SARB are adjusted according to this methodology