The effect of potassium lactate treatment on the shelf life of vacuum-packaged fish was studied. Chub mackerel was treated with 2% and 4% potassium lactate solutions, and their shelf lives were compared with those of control (not treated) samples. Samples were stored at 4degreesC and sensory evaluation, and chemical and microbiological analyses were done every three days. Control group spoiled after six days of storage. The addition of potassium lactate decreased microbiological activity and treated samples remained in good quality until the ninth day of storage. There was no significant difference between the shelf life of samples treated with either 2% or 4% potassium lactate. These results indicate that treatment with potassium lactate extends the shelf life of vacuum-packaged and refrigerated chub mackerel.