abstract the leaves of thymus fallax fisch. et c.a. mey. were collected from hamedan (the center of hamedan province) in the west of iran and hydrodistilled to produce a light-yellow oil at the yield of 2.5% (based on dry leaves). the oil was analyzed by gc and gc/ms. twenty-three compounds were identified, among which thymol (65.9%) and -terpinene (10.8%) were the major constituents.