The paper deals with the plague epidemic that in 1631 crossed the borders of the Duchy of Carniola from the west, affecting especially Loška Dolina, Loški Potok, and villages along the upper course of the Reka River. The main source for the research was the Provincial Estates’ Registry Protocol, which contains three direct and several indirect refer-ences to the spread of the contagious disease in the territory of the present-day Municipality of Ilirska Bistrica: between August and November 1631, the epidemic was recorded in Zabiče, Podgraje, Kuteževo, and Zemon. The Provincial Estates of Carniola attempted to prevent the spread of the disease by deploying plague guards, who first took control of the provincial borders in July; in August, they began to isolate the infected areas within the province itself and remained in place at least until November. Two documented barriers were set up by hired soldiers within the province: one at the northwestern edge of Loška Dolina and the other at an unknown location in the Reka River valley.