The article considers the sphere of illicit trade, partly suppressed, partly tolerated, that emerged amongst the inhabitants of post-war Poland and Czechoslovakia. It developed soon after the Second World War because of a combination of geographical, historical, social, economic, and political conditions, and considerably expanded with time, particularly in the 1970s and 1980s. It followed on from the earlier practice of smuggling, which had been possible primarily because most of the frontier between the two states (from Racibórz in the east) had been left largely unchanged since the Middle Ages, running through hard-to- access mountain terrain inhabited by mountain people, for whom smuggling had long been a source of livelihood. It was only on this border, in Poland in the late 1950s, that the existence of ‘professional smugglers’ was confirmed. The escalation of smuggling here was also influenced by the relatively quick development of tourism between the two states, after the signing of a 1955 agreement on relations in the border zones, and also by the convenience of illicit exchange for Poles and Czechoslovaks, since economic shortages were manifested differently in each country. One of the traditional items of illicit trade amongst the mountain people was farm animals (especially horses), which in Poland were less expensive than in Czechoslovakia, and, from the mid-1950s onward, gold and hard currency, as well as building materials, which were in extremely short supply in Poland. Tourists ‘underhandedly’ exported or imported a wide variety of goods, mainly textiles, footwear, foodstuffs, alcohol, cigarettes, and electric household appliances. The informal ‘tourist exchange’ between Poland and Czechoslovakia expanded from the traditional areas of the Tatra Mountains also to the Giant Mountains (Krkonoše in Czech, Karkonosze in Polish, Riesengebirge in German) and, in the late 1960s and early 1970s, their centres were Katowice, Zakopane, and Nowy Targ. The development of illicit trade led, from the mid-1970s, to the fact that the Czechoslovak side in particular (similarly to East Germany, for example) took measures to restrict this trade (for instance, putting bans on the export of various goods) and also undertook repressive operations (including uncompromising customs checks and confiscation of goods). Other factors were political unrest, the intensifying economic crisis, and eventually, in the 1980s, the complete lifting of travel restrictions on Poles. At the end of this period, problems with illicit trade were reflected also in the worsening diplomatic relations between the two countries.