Cold-acclimated, fifth-instar P. interpunctella collected from pre-established overwintering sites were used to determine the effect of winter temperatures on larval mortality. On November 2003 larvae were released inside four 3000-bu grain bins filled with corn, located at Rosemount, MN. Larvae were monitored at two locations (center and southern edge) within each bin and two depths (5 and 40 cm) at each location. Each of two bins received a temperature treatment (i.e., by fan aeration) of either -7 to -4ºC or -1 to 2ºC, whenever the air temperatures were within these ranges. Larvae were removed approximately every 15 d to determine mortality. Larval mortality increased with time at all locations in all grain bins. However, the center of the bin appeared to offer better protection to larvae compared to that offered by the edge of the bin, where temperature fluctuations were greater. In addition, the 40 cm depth appeared to give better protection to larvae than that offered by the 5 cm depth. Larval mortality reached 100% in all experimental locations by late February 2004. As a result of the temperatures experienced at the experimental sites, results suggest that cold-acclimated fifth-instars are chill-tolerant and that mortality may have occurred as a result of the accumulation of chill injuries rather than freezing. A better understanding of how well P. interpunctella tolerates low temperatures may help us to expand the opportunities for controlling this pest in granaries and other food-storage systems in the winter.