According to I. Schipper already in the second half of the 16th century Jews dominated in foreign trade and in many branches of domestic trade in Poland. The 1620s and 1630s witnessed a major credit crisis, which preceded a decline of trade in the mid 16th c. On the other hand, R. Rybarski concludes that in the mid 16th century the proportion of Jews in trade was generally low. According to the records of the Warsaw customs house from 1605-1651, Jews constituted only 6.2% of all the merchants. In 1604 Cracow had 47 Jewish merchants (9.8% of all the traders), whose turnover constituted less than 3% of the town's global exchange. Cracow customs records indicate that Jewish commodities were about 5% of all the cargos in 1593 and 9-10% in 1636. The article is based mainly on Cracow records from the years 1601-1604, 1615-1619, 1641-1645 and 1649-1651. In the years 1641-50 the number of Jewish cargos decreased in comparison with 1615-19. In 1649 470 Jewish cargos were registered in domestic trade and 115 in foreign trade. In 1650 347 cargos were recorded in domestic trade, including 98 in exchange with towns located in Little Poland, 68 with towns in Red Ruthenia, 29 with towns in Great Poland, 25 with towns in Mazovia and 127 with unspecified towns. The total number of cargos registered in that year was 4965. Cracow's trade with Leipzig in the years 1649-51 was monopolized by Scottish merchants from Cracow and Poznan. A more thorough analysis was undertaken of transactions between Jewish merchants from Sandomierz and Cracow. The dynamic development of the exchange is evidenced by the average annual numbers of cargos: 109 in 1593, 56 in 1636, 80 in 1601-1604, 132 in 1615-1619, 77 in 1641-1645 and 52 in 1649-1650. Throughout the period commerce was dominated by Christian (Polish and Scottish) merchants, with the exception of Opatów and Pinczów, where Jewish traders were the majority.The claim that in the mid 17th century Jewish trade was in decline is definitely exaggerated - there is clear counterevidence in the records of the customs house in Dybów near Torun (Thorn) from the years 1656-1658. In the last quarter of the 17th c. many Jewish merchants from Poland could be met at fairs in Leipzig and Wroclaw (Breslau). At that time Jews began to dominate in Polish commerce, especially in foreign trade.