Abstract: Room temperature vulcanizable polyorganosiloxane composition comprising (A) 100 parts of polydiorganosiloxane in which 0.1 to 25 mole percent of the total organo groups that are attached to silicon atoms are phenyl groups, and having a viscosity of 100 to 1,000,000 cSt at 25.degree. C., and in which silanol-terminated polydiorganosiloxane constitutes more than 60 weight % of the total, (B) 0.1 to 50 parts of an organic silicon compound containing aminoxy groups, (C) 75 to 300 parts of aluminum hydroxide powder having a size of less than 50 microns and (D) 0.000001 to 0.005 parts, calculated platinum, of platinum or a compound thereof. The composition is curable at room temperature whereby it gives an elastomer having low modulus, high elongation, and a self-extinguishing property.