Although insect damage to bamboo materials in buildings has grown considerably recently, there has been very little scientific research on chemicals for preventing it. The authors first recorded reported examples of insect damage to bamboo materials, then conducted a screening test for effective insecticides. They found that two low-toxic organophosphorus pesticides, prothiophos emulsion and phoxim emulsion, had superior insecticidal proper ties as compared to organochlorine-type insecticides. Finally, an effective method for preventing such insect damage is shown.