Abstract The essential oils obtained by hydrodistillation of the stem and leaf of Mentha aquatica L. and the aerial parts of Nepeta meyeri Benth., two Labiatae species of Iran, were analyzed by GC and GC/MS. Twenty compounds, representing 88.1% of the stem oil of M. aquatica, were identified; among them β-caryophyllene (22.4%), viridiflorol (11.3%) and 1,8-cineole (10.9%) were the major ones. The leaf oil of the plant was characterized by higher amount of piperitenone oxide (25.7%), and also β-caryophyllene (12.0%) and 1,8-cineole (10.3%), among the 29 components, comprising 95.4% of the total oil, detected. The oil of N. meyeri was made up mainly of oxygenated monoterpenes, of which 4aα,7α,7αβ-nepetalactone (68.1%) was the major constituent.