An alkaliphilic Streptomyces strain Marac 1-4, producing an alkaline protease, was isolated from a marine sediment sample in Izmir gulf. The protease production was performed in a medium containing seawater (SWFM) and distilled water (FM), respectively, and its activity was found to be significantly higher in SWFM than in FM (p<0.1). Amono, the 11 carbon and 8 nitrogen sources, the best enzyme activity was obtained by sucrose and peptone, respectively. The enzyme was found to be stable in the presence of various oreanic solvents with log P-o/w values between 3.1 and 5.6, and showed better activity than nonsolvent-containing control. Seawater in production medium was necessary for its better activity and stability in the presence of organic solvents.