S. The effects of high intensity pulsed electric field (HIPEF) treatments at room or moderate temperature on water-soluble (thiamine, riboflavin, ascorbic acid) and fat-soluble vitamins (cholecalciferol and tocopherol) were evaluated and compared with conventional thermal treatments. Vitamin retention was determined in two different substrates, milk and simulated skim milk ultrafiltrate (SMUF). Samples were subjected to HIPEF treatments of up to 400 µs at field strengths from 18n3 to 27n1 kV\cm and to heat treatments of up to 60 min at temperatures from 50 to 90 mC. No changes in vitamin content were observed after HIPEF or thermal treatments except for ascorbic acid. Milk retained more ascorbic acid after a 400 µstreatment at 22n6 kV\cm (93n4 %) than after low (63 mC-30 min ; 49n7 % retained) or high (75 mC-15 s ; 86n7 % retained) heat pasteurisation treatments. Retention of ascorbic acid fitted a first-order kinetic model for both HIPEF and thermal processes. First-order constant values varied from 1n8i10 −% to 1n27i10 −$ µs −" for the HIPEF treatments (18n3-27n1 kV\cm) and, for thermal processing ranged from 5i10 −$ to 8i10 −# min −" (50-90 mC). No significant differences were found between the results obtained after applying HIPEF treatments at room or moderate temperature. However, results depended on the treatment media. A beneficial effect of natural skim milk components, mainly proteins, was observed on the preservation of ascorbic acid, since skim milk retained more ascorbic acid than SMUF after HIPEF treatments.