Egyptian mummies show different signs of deterioration caused by insects. Dermestes maculatus is one of the serious pests that cause damage to Egyptian mummies. To assess the insecticidal activity of cedar wood oil against the larvae of the museum insect pest Dermestes maculatus (isolated from Egyptian mummies) we test-ed it under different concentration and treatment times by the bioassay methods. Our results showed that cedar wood oil diluted in ethanol had a toxic effect on 4th instars larvae of Dermestes maculatus larvae. Insec-ticidal activity depended on both concentration and exposure time. By increasing the concentration level and the exposure time we obtained a higher mortality rate.