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Epilobium minutiflorum belongs to the genus Epilobium with important medicinal properties. In this study, the natural variation of phytochemical compounds of E. minutiflorum at different altitudes has been investigated. Aerial parts of plants were collected at flowering stage from natural habitats at different altitudes of 2387, 2569 and 2813 masl. The plant extracts were obtained with 80% methanol and several phytochemical properties were measured. The properties included the total flavonoid content (TFL), total phenol (TPH), antioxidant capacity (AOX) and anthocyanin content (ACY) measured by the AlCl3, the Folin-Ciocalteu, the Ferric reducing antioxidant power (FRAP) and the differential PH methods, respectively. In addition, phytochemical components were identified by the GC/MS method. The results of photometric analysis indicated that the population of Shemshak, located at the highest altitude showed the highest content of TFL, TPH and AOX with 30.39 mg/gr DW, 938.91 mg/gr DW and 77.77 mM/gr DW, respectively. The TFL, TPH and AOX values showed a positive correlation with altitude. The results of GC/MS analysis revealed the presence of 41 compounds in E. minutiflorum, which were separated into flavonoids, phenolic acid and its derivatives, steroids and terpenes groups. Shemshak population showed the highest value in all identified compounds. A positive correlation was also observed between altitude and 30 compounds identified by the GC/MS method including mainly flavonoids and phenolics. The results of this study indicated that environmental factors at higher altitudes may influence the elevation of the flavenols and phenol content in E. minutiflorum. The identification of these influential factors on phytochemical content at higher altitudes requires further studies.