This compilation of potassium-argon (K-Ar) ages of igneous rocks of the Tertiary volcanic field of Trans-Pecos Texas includes all published ages known to us as well as many unpublished results. Almost all age determinations and all published ages of Trans-Pecos rocks are by the K-Ar method, so this compilation essentially includes all isotopic age information. It expands upon an earlier summary by McDowell (1979) by including the considerable number of analyses done since then and by tabulating available rock type, analytical data, and location information. Where appropriate we have briefly discussed the significance sf the ages, especially to point out obviously unreasonable ages.