Abstract The composition of the essential oils from leaves and seeds ofBlepharocalyx tweediei and B. gigantea, two closely related taxa from Argentina, was determined by capillary GC, GC/MS and 13C-NMR. The main compounds in the oils of B. tweediei were Î±-and Î²-pinene, 1,8-cineole and limonene, linalool being also a major constituent of the oil from leaves. The oils from B. gigantea were characterized by a high percentage of 1,8-cineole, followed by Î²-pinene and viridiflorol.