ABSTRACT: Stewed beef and grilled dry aged beef were analyzed as part of an in-depth analytical program, with the aim of creating new flavors incorporating only compounds identified in the target foods and identifying new synthesis targets. In-house GC-MS analyses of several types of cooked beef have identified over 1000 volatile and semivolatile components; many for the 1st time. Among the semivolatiles detected were ten 2, 5-diketopiperazines (cyclic dipeptides) previously unreported in beef. These cyclic dipeptides are cis-cyclo(l-Ile-l-Pro), cis-cyclo(l-Leu-l-Pro), cis-cyclo(l-Pro-l-Pro), cis-cyclo(l-Pro-l-Val), cis-cyclo(l-Ala-l-Pro), cyclo(Gly-l-Pro), cyclo(Gly-l-Leu), cis-cyclo(l-Met-l-Pro), cis-cyclo(l-Phe-l-Pro), and cis-cyclo(l-Phe-l-Val). All 10 cyclic dipeptides were synthesized and evaluated organoleptically. Among them cis-cyclo(l-Leu-l-Pro), cis-cyclo(l-Met-l-Pro), and cis-cyclo(l-Phe-l-Pro) were found to be of particular organoleptic interest.