The efficacy of methyl bromide (MB) and sulfuryl fluoride (SF) for managing all life stages of the red flour beetle, Tribolium castaneum, was investigated in the Hal Ross Flour Mill at Kansas State University. Eggs, young larvae, large larvae, pupae, and adults, confined in plastic compartments with dusting of flour and 2-cm deep flour, were exposed at 25 mill locations to two MB and two SF fumigations; in May and August 2009. MB and SF treatments were conducted by commercial fumigators, and each fumigation lasted 24 h. Gas monitoring lines were placed near the bioassay boxes to measure gas concentrations over time during fumigations. Both MB treatments killed 100% of all stages in the boxes except for large larvae in a few locations. In these locations, the mortality of large larvae ranged from 96-98%. SF treatments killed 100% of all stages except eggs. In the May treatment with SF, egg mortality ranged from 44-100% with only two boxes showing 100% mortality, because of under-dosing. Under-dosing occurred because the mill temperature was assumed to be greater than 27ºC when it was actually below 27ºC. In the second SF trial, only three boxes had egg mortalities that were less than 100%. However, data from the two replications showed that the mean mortalities of eggs and large larvae between MB and SF were not significantly different from each other.