Book louse Liposcelis bostrychophila is a minor pest in stored products, and may seriously infest the stored products when its population outbreaks. This study was conducted to evaluate the toxic effect of DDVP on various development stages of L. bostrychophila. The results showed that at 28 +/- 0.5 degrees C and 24 h exposure under 75%-80% RH, the LC50 of the eggs, larvae of 1st to 4th stadium, and adults was 16.83, 0.22, 0.22, 0.23, 0.26 and 0.25 micrograms.L-1, respectively. The lethal effect of DDVP on the adults at different exposure periods showed that their mortality was linearly related to the treated time, implying that the test colony of L. bostrychophila was susceptible to DDVP. In the practical fumigation, DDVP as a fumigant had a good effect on the pest control if the development stage, time and periods of treatment were appropriate.