Background and aim: The genus Satureja L. (Lamiaceae) includes 12 species of annual and perennial herbaceous plant in Iran. Satureja species have economic and medicinal importance because of their high essential oil content. In addition, they are used as culinary herbs and in the food, perfume and cosmetic industries. The aim of this study was to investigate the effect of sowing date and plant density on the quantity and quality yields of Satureja hortensis L. essential oils in Sari climatic condition. Experimental: A field experiment was conducted in Sari Agricultural Sciences and Natural Resources university by using of split-plot design in the base of randomized complete blocks with three replications in 2010. Main factors were three sowing dates (11 April, 22 April and 3 May) and sub factors were three plant density (15*35, 25*35 and 35*35cm). The plants were investigated in full flowering stage. Aerial parts of the plant were subjected to Hydro-distillation for 3 h using a Clevenger-type apparatus to produce essential oil. Chemical compositions of the essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS). Results and discussion: Sowing date had significant effect on essential oils content and dry shoot yield. The result of mean comparison showed that first sowing date had highest essential oils content (2.15) and delay in sowing time increased dry shoot yield significantly(p<0.05). The dry shoot yield (3023.1 and 2663.9 kg/h) at third and second sowing times was the highest. Plant density and interaction of sowing date and plant density had no significant effect on dry shoot yield and essential oils content. The results indicated that the essential oil yield and main essential oil components (carvacrol, γ-terpinene, ρ-cymene, α-terpinene and camphene) were not affected by sowing date and plant density. Industrial and practical recommendations: Dry shoot yield, essential oil and main constituents of the essential oils of Satureja hortensis L. can be increased with good management and choose of suitable solutions. تفاصيل المقالة