The ability of high hydrostatic pressure treatment (HHPT) to extend the shelf life of Atlantic mackerel (Scomber scombrus) was assessed in this study. For that purpose, fillets were subjected to pressure treatments at 200, 300, 400 MPa at 5, 10, 15 A degrees C for 5 and 15 min. The influence of pressure treatments on the levels of trimethylamine nitrogen (TMA-N) and thiobarbituric acid (TBA) as well as color changes was investigated. The suitable combinations were determined as 200 MPa, 15 A degrees C for 5 min. and 400 MPa, 5 A degrees C for 5 min. In the second stage, the shelf life of samples, which were treated at these conditions, stored at 4 A +/- 0.5 A degrees C were studied by monitoring pH, color, sensorial features (appearance and odor), TMA-N, TBA, total volatile basic nitrogen, histamine, and total mesophilic aerobic count. The unpressurized mackerel samples were acceptable up to only 7 days compared to 17 and 19 days after 200 and 400 MPa treatments; respectively. The results obtained in this study showed that HHPT in combination with chilled storage can improve the shelf life and quality of fish.