The effect of ozone on the respiration of three species of adult stored-product Coleoptera was tested in an air-tight flask. Sitophilus oryzae (L.), Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst) adults were exposed to atmosphere containing 0.1, 0.2 or 0.4microg/ml initial ozone at 23-25 degrees C and 50% r.h. Carbon dioxide (CO(2)) production reflected the respiration rates of insects and was determined with a gas chromatograph (GC). The experiments showed that the effects of ozone on respiration had two distinct phases. Phase 1 involved a lower respiration rate of the adult stored-product Coleoptera under ozone atmosphere and reflected the need for insects to reduce ozone toxicity. After 1h, CO(2) production of S. oryzae was 3.19, 2.63, 2.27 and 1.99microl/mg for the ozone concentration of 0, 0.1, 0.2 and 0.4microg/ml, respectively. The results also showed that there were decreases in the rate of respiration in R. dominica and T. castaneum with an increase in ozone concentration. During phase 2, respiration of S. oryzae, R. dominica, and T. castaneum adults treated with ozone increased as the ozone degraded to oxygen. After 7h, the effect of ozone on CO(2) production, relative to the control, changed from a decrease to an increase. The findings in relation to control strategies were discussed.