Eighty-four collections of 51 species of Middle-eastern Cruciferae were analysed by paper and gas-liquid chromatography for seed glucosinolates. ThirW-two species were investigated for the first time. Thirty compounds were identified and three unknowns of limited occurrence were found, p-Hydroxybenzylglucosinolate was found in six species of various tribes. 4-Methylsulfinyl-3-butenyl, 3-methoxycarbonylpropyl, and p-rhamnopyranosyloxybenzyl glucosinolates, which are rare in the Cruciferae, were found in Sinapis aucher~ two species of Erysimum and Thlaspiperfoliatum, respectively. The biosynthetic precursors of all but one of the 30 glucosinolates are protein amino acids and at least 20 glucosinolates are derived from methionine. The distribution of giucosinolates is very useful at the species and genus levels but may provide only minimal support to the tribal alliance of certain genera. It supports the removal of Sinapis aucheri from the genus, the recognition of Fibigia clypeata and F. macrocarpa as distinct species, and the alliance of Ochthodium with Euclidium and Arabis with Drabopsis.