Background. It is necessary to develop a balneotherapeutic and tourist-recreational complex on Iturup Island (hereinafter referred to as Iturup Island). This investigation was conducted in the framework of the federal target program «Socioeconomic development of the Kuril Islands, Sakhalin Region, for 2007—2015» under No. 478 dated 08.09.06. Objective — to characterize the balneological resource of the «Zharkie Vody» (Hot Water) spring on Iturup Island. Material and methods. Expeditionary studies were conducted at the «Zharkie Vody» spring located near the village of Raidovo (Iturup Island): its water samples were taken and chemically analyzed in a certified laboratory in Khabarovsk; the biological activity of the mineral water was studied using the Cyto-Expert portable non-invasive diagnostic equipment adapted to the expeditionary conditions. Results. The mineral water from the «Zharkie Vody» deposit (Iturup Island) is weakly mineralized siliceous sulfate-bicarbonate-chloride calcium-sodium thermal and has an activation function on living cell structures. Conclusion. The data obtained from the studies created the prerequisites for setting up a balneotherapy complex near the «Zharkie Vody» on Iturup Island and provide optimistic forecasts for the further study of this deposit.