Studies were carried out in 2003–2005. The dependence between harvest date and yielding of marjoram (cv. ‘Miraż’) was investigated. The plantation was set from a seedling produced in a greenhouse. Plants were set in 30 × 40 cm spacing. Two weeks after setting, part of plants were cut and shoot tips with the first leaf pair were removed. The herb harvest was made twice: in the middle of July and at the end of August. Ground herb was subjected to determinations of essential oils. Qualitative and quantitative composition of marjoram oil was determined by means of gas chromatography coupled with mass spectrometry (GC/MS). The harvest date had significant influence on marjoram yielding. Higher yield of a fresh herb was achieved at the end of August (44.6 dt^.ha^-1) than in the middle of July (30.5 dt^.ha^-1). The essential oil content in the herb of marjoram cv. ‘Miraż’ was 1.7–2.2%. Trans-sabinene hydrate, terpinen-4-ol, and sabinene dominated in marjoram essential oil.

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