Peppermint (Mentha piperita cv. Mitcham) plants were grown in Investigative Field of Ferdowsi University of Mashhad in IRAN (59 N latitude),and evaluated for their response to nitrogen rates. The form of applied nitrogen was urea. Plants were measured for total dry weight, final plant height, nodes number, internode length, total leaves number, and essential oil content in flowering stage. Rates of nitrogen applied were 0 (control), 75,150, and 225 Kgha-1nitrogen. Each treatments had three replicate. It was established that plant dry mater, plant height, internode length, leaves number, node number, and essential oil content were increased with increasing nitrogen rates (with the exception at 225 Kgha-1N). With the increased fertilizer rates, the essential oil yield of the treated plants increased compared to the control. The highest and lowest essential oil content were shown in the plants that received 150 and 0 Kgha-1N, respectively.

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