The objective of this study was to determine the biomechanical and microbiological effects of exposing natural hog casings to ozonated water approximate to 7 mg/l for 0, 2 or 4 h at 16 degrees C. A total of 450 casing segments representing 10 hanks were used over five testing days and arranged in a randomized block split-plot design. For each treatment, pH, temperature, actual ozone concentration, bursting strength, maximum rupture force, and L*, a* and b* color space values were determined. The bursting strength and the maximum rupture force values suggested that casings can be treated by ozone up to 2 h without deterioration. After ozone treatments, changes in L*, a* and b* color space values made the casings appear lighter than the control samples. Microbiological studies showed that I and 2 h ozonation reduced counts of Escherichia coli biotype 1, which expressed green fluorescent protein, by 0.4 and 0.6 log(10) CFU/25.4 cm casing, respectively.