Technical Abstract: With the uses of methyl bromide becoming fewer as we approach the cutoff year of 2005, new and inventive alternatives to those uses are becoming more important. In 1999, we began to investigate the possibility that ozone could replace some fumigant uses by methyl bromide against postharvest insect pests. We first found that ozone produces mortality throughout the life stages of the insect even though exposure was to the egg or larval stages. We also found that carbon dioxide enhanced the toxic effects of the ozone. In 2001, we entered into a cooperative agreement to conduct research on the use of ozone combined with carbon dioxide and/or vacuum to control postharvest insects. We began by attempting to discover the most tolerant stage of a common moth and beetle pest. We chose the Indianmeal moth, Plodia interpunctella (Hübner), and the confused flour beetle, Tribolium confusum Jacquelin du Val, to be representative of the 2 common postharvest insect pests with ozone, carbon dioxide and vacuum. Using an ozone concentration ranging up to 10,000 ppm (v/v), a carbon dioxide concentration of 5 to 7%, a vacuum of '10 in. Hg, and a 2 hour exposure, we found that with both insects, the egg stage was the most tolerant stage. We then began to look for areas where ozone might be used as a treatment to replace methyl bromide. Currently we are investigating the possible use of ozone to kill bean thrips, Caliothrips fasciatus (Pergrande), in the navel of navel oranges where they overwinter and present a problem to the export of California navel oranges to Australia. In addition, we are investigating the uses of ozone to control the coffee berry borer, Hypothenemus hampei (Ferrari) in coffee beans being imported into the United States. We have found that efficacious insecticidal results can be obtained with ozone combined with carbon dioxide and vacuum while not being phytotoxic to the commodities on which they are feeding.