Abstract Origanum majorana L. (Lamiaceae) has two chemotypes in Turkey. The type growing in the southwestern part of the Mediterranean region is characterized by rich oil yield and high carvacrol content. This type known as 'beyaz kekik' (white oregano) and is commercialized. The more usual sweet marjoram (mercankÃ¶sk) type of O. majorana grows in the western part of Turkey. This type is poor in oil and contains only trace amounts of carvacrol. cis-Sabinene hydrate (30â44%) and terpinen-4-ol (8â14%) were found as main constituents in the Turkish materials collected in different periods of vegetation. Origanum x majoricum Cambess. is a known hybrid of O. majorana L. x O. vulgare L. ssp. virens (Hoffm. et Link) Ietswaart and is also cultivated in Turkey. Sweet marjoram contains cis-sabinene hydrate (24â37%) and terpinen-4-ol (6â13%) in its oil. Key Word Index: Origanum majorana Origanum x majoricum Lamiaceaeessential oil composition cis-sabinene hydrateterpinen-4-ol