In Japan, phosphine resistant cigarette beetles (Lasioderma serricorne (F.); Coleoptera: Anobiidae) have been observed occasionally since 1996. Phosphine's insecticidal activity is affected by its concentration, temperature and the duration of fumigation. It was supposed that a higher concentration, temperature or longer duration would be required to control phosphine resistant cigarette beetles. In order to examine the phosphine treatment conditions needed to control phosphine resistant cigarette beetles, we investigated the phosphine's insecticidal activities against a phosphine susceptible strain and a resistant strain at various fumigation conditions. Overall, a much higher concentration was required to control the resistant strain. For both of the strains tested, a high phosphine concentration and a long fumigation duration were required to kill them at 15 °C or less. It was also found that the higher the temperature was, the more effective the insecticidal activity was and that if the temperature was kept at 25 °C or more and fumigation was continued for 4 days or more, it would be possible to exterminate cigarette beetles totally at a relatively low phosphine concentration.