The use of aseptic, non-denatured fresh ground beef did act as an useful tool in evaluating meat microbiology. The pH values did not change significantly in any of the treatments except for the treatments with higher Pseudomonas inoculation level and after 7 days of storage. The inoculation of difference levels of Pseudomonas and E. coli showed significant difference with their PIA and VRBA counts. However, the numbers of VRBA counts in the 4 log E. coli had only a slightly higher counts than those of 2 log E. coli even though there was a significant difference (P < 0.05). This data indicates that the growth of 2 log E. coli increased but the growth of 4 log E.coli could have been affected. The adding of either 2 log or 4 log of E. coli in the treatments with 3 log or 6 log Pseudomonas inoculation did not significantly affect total plate counts (TPC). However, without the adding of background Pseudomonas, the adding of 2 log or 4 log E. coli did cause a difference in the PCA counts. There is no significant difference between the adding of 2 log or 4 log E. coli at any Pseudomonas levels. This results might imply that the adding of 4 log E. coli did not have as much added increase in the numbers of E. coli counts as the 2 logs of E. coli. This might mean that the adding of 4 log of E. coli had been surpressed by the background Pseudomonas. Therefore, for futher experiemnts, the adding of 4 log of E.coli will be used since the growth of 4 log of E. coli did not show a large increase in numbers compared to 2 logs of E.coli adding at any Pseudomonas levels.