The Indianmeal moth, Plodia interpunctella (Hübner), was selected as a representative stored-product moth to test the validity of contour mapping of trap catch for pest monitoring in warehouses and retail stores. Three experiments, each replicated five times, were conducted in a 3.2 by 9.0-m aluminum shed. Each experiment involved placing pupae at a single release point (source) and recording the numbers of emerging adult males captured after 24, 48, and 72 h in each of four pheromone-baited sticky traps. The experiments differed only with respect to the point of release. Distribution of trap catch reflected the general distribution of moths in the shed; and consecutive contour maps tracked their dispersal from the source. As emergence and dispersal progressed, cumulative trap catch increased throughout the shed, but it remained highest near the source. The observed spatial patterns of trap catch relative to sources of infestation and the inverse relationship of trap catch to distance from a source support the validity of contour mapping as a means of monitoring stored-product moths and locating foci of infestation. The relationship between trap catch and distance from a source of infestation was well described by two-parameter exponential decay, both in P. interpunctella and in the previously studied Lasioderma serricorne (F.). Analysis of data from retail pet stores also showed exponential decline in trap catch of P. interpunctella with distance from centers of infestation.