Research on foreign trade in the Polish-Lithuanian Commonwealth in the second half of the 18th c. has been largely neglected for many years, and the basic findings in that area, especially those by Tadeusz Korzon, suggest that the problem should be reconsidered. The topic requires new research first of all in order to verify the unfounded theses about the downturn in the economy being one of the reasons of the political crisis and the fall of the country. This claim seems to be contradicted by the long-established theories about the development of the country's economy, including foreign trade, in the period before the partitions. In view of that, it is difficult to maintain that the recession was one of the reasons of the partitions; it should rather be assumed that it was largely a result of the actions undertaken by the partitioners, especially by the king of Prussia Frederick II. New material to research the topic can be found in the numerous and interesting initiatives to improve the situation in trade which were voiced by publicists at the end of the 18th c. It is also significant that income from customs duty was very important for the state budget. New data can be obtained from the surviving balance sheets of the exports and imports of the Crown of Poland in the years 1786-1790. The article discusses only one of those documents. The data show very precisely the scale of exchange between the Crown and its closest neighbours, i.e. Austria, Prussia and Russia, Turkey and Wallachia taken together. They also point to very characteristic tendencies in foreign trade, including the transit of commodities.