This paper discusses different categories of unrecorded alcohol consumption and the data sources used in estimating their magnitude and developments. It also gives a brief overview of the developments and importance of different categories of unrecorded alcohol consumption in Finland in the post Second World War period until the 1990s, and a more detailed analysis of the developments in the 1990s. One of the main findings is that travelers' alcohol imports have gained in importance, especially during the 1990s. However, drinking of non-beverage alcohol or surrogates has almost disappeared on the Finnish alcohol scene. In the second half of the 1990s homemade alcohol was also on the decrease. At the end of the 1990s about one-fifth of all alcohol consumed was unrecorded alcohol. More than half of the unrecorded alcohol consisted of travelers' alcohol imports. The next important categories were consumption outside Finland, homemade alcohol, and smuggled alcohol.