The objective of this study was to investigate and compare the effects of UV light and heat treatment on vitamins A, B-2, C, and E in cow and goat milk. Vitamins were analyzed by reverse-phase high-pressure liquid chromatography. Ultraviolet and pasteurization treatments caused loss in vitamin C in milk. Pasteurization did not have any significant effect on vitamin B-2. However, UV light treatment decreased the amount of vitamin B2 after several passes of milk through the UV system. In addition, UV light treatment decreased the amount of vitamins A and E. Vitamins C and E are more sensitive to UV light. UV light sensitivities of vitamins were C > E > A > B-2. These results show that UV light treatment decreases the vitamin content in milk. Also, the number of passes through the UV system and the initial amount of vitamins in milk are important factors affecting vitamin levels.