Technical Abstract: Pseudomonas aeruginosa, a common spoilage microorganism on fresh catfish products, can grow rapidly at temperatures above 4 degree C during storage and transportation. Allyl isothiocyanate (AIT), an extract of horseradish oil, and modified atmosphere (MA) can be used to inhibit the growth of P. aeruginosa on fresh catfish fillets during storage. The objectives of this research were: 1) to investigate the antimicrobial effect of vapor phase AIT and MA on P. aeruginosa groeth in fresh catfish fillets; and 2) to develop models to predict the shelf-life of fresh catfish products following the application of AIT and MA. Three concentrations (0, 18 and 36 ppm) of vapor phase AIT were used to inhibit the growth of a P. aeruginosa cocktail (3-strains) inoculated onto catfish fillets at 8, 15 and 20 degree C. In addition, the antimicrobial capability of MA (50% CO2, 49.5% N2 and 0.5% O2), and MA combined with AIT, were also investigated. Our results showed that lowering storage temperature as well as increasing AIT concentration could elongate the lag phase and reduce the growth rate of P. aeruginosa. In addition, AIT alone reduced P. aeruginosa counts within first several hours. Our results also indicated that application of MA had a similar antimicrobial effect as lowering storage temperature. Therefore, to attain a longer shelf life of fresh catfish fillets, the combination of AIT and MA was included in this study. The synergistic effect of AIT and MA may extend the shelf life of fresh catfish from 4 days (untreated control) to 13 days at 8 degree C. Models developed from this study may be applied to estimate the lag phase and growth rate of P. aeruginosa under temperature abuse conditions. These results could assist the food industry predict tcatfish product shelf-life, which may be further optimized with the proper AIT concentration in a MA package.