Summary A study has been made of three groups of samples fortified with a vitamin A concentrate—sesame oil, margarine stock, and a mixture of 95% margarine stock and 5% sesame oil—to determine the stability of vitamin A in the presence of sesame oil. The samples were stored at two temperatures and their vitamin A content was measured periodically throughout a period of 42 weeks by an ultraviolet absorption method. The results show no evidence of vitamin A instability in the three groups of samples after storage at 32°F. for 42 weeks, or in the margarine stock and margarine stock‐sesame oil mixture after storage for the same period of time at 78°–80°F. However the pure sesame oil showed a significant change in vitamin A content at the end of 42 weeks of storage at 78°–80°F. The trend toward instability became evident after 13 to 26 weeks of storage.