Exposure of a pyrethroid-susceptible strain of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae) to varying concentrations of deltamethrin for 24 h indicated no significant difference in mortality between males, females, and nymphs at 24 nor at 168 h postexposure when bed bugs were removed to untreated surfaces at 24 h. In addition, many bed bugs classified as morbid or moribund at 24 h and removed to untreated surfaces at this time, recovered by 336 h (2 wk) and were capable of feeding when given the opportunity. Adult female bed bugs that survived were able to lay eggs and the resulting nymphs blood-fed. By contrast, all bed bugs classified as morbid or moribund at 24 h that remained on deltamethrin-treated surfaces for 336 h either died or were still classified as morbid or moribund at the end of this time. No bed bugs classified as morbid or moribund blood-fed when given the opportunity at 2 wk, regardless of whether they remained on the treated surfaces or were removed to untreated surfaces. A power analysis demonstrated we would have detected even moderate differences in mortality between males and females, had differences existed. Therefore, using males exclusively in efficacy assays is a suitable strategy to preserve females for laboratory colony purposes. Results also indicated there is little reason to assess efficacy beyond 1 wk, even when bed bugs are exposed for only 24 h.