A silicone elastomer composition adapted for use as a dental impression material, which provides a rubber mold having the total light transmittance for a thickness of 2 mm of at least 90%, a hardness, as measured with a type A durometer, of at least 10 and not more than 30, a tear strength determined according to JIS K6249 of at least 0.8 kN/m and not more than 2.0 kN/m and an elongation at break determined according to JIS K6249 of at least 150% and not more than 300%, after curing said silicone elastomer composition, the composition comprising: 100 parts by weight of a diorganopolysiloxane has an average degree of polymerization of at least 300 and less than 3,000 and contains at least two silicon atom-bonded alkenyl groups per molecule and has a viscosity at 23°C of from 2 to 200 Pa·s, from 10 to 100 parts by weight of a diorganopolysiloxane which has an average degree of polymerization of less than 300 and contains at least two silicon atom-bonded alkenyl groups per molecule and has a viscosity at 23°C of from 20 to 2,000 mPa·s, from 10 to 200 parts by weight of a diorganopolysiloxane which has an average degree of polymerization of 3,000 to 30,000, contains at least two silicon atom-bonded alkenyl groups per molecule and is gum-like at room temperature, from 5.0 to 20 parts by weight of an organopolysiloxane which consists of units selected from the group consisting of R 3 SiO 1/2 units (M units), SiO 4/2 units (Q units), R 2 SiO 2/2 units (D units) and RSiO 3/2 units (T units), contains M units and Q units as essential constituent units, has a combined amount of M units and Q units that is at least 80 mol % of all constituent units, and has a (number of moles of M units) / (number of moles of Q units) ratio in the range of 0.5 to 1.5 wherein R is a monovalent hydrocarbon group of 1 to 6 carbon atoms, and at least two R groups per molecule are alkenyl groups, an organohydrogenpolysiloxane which contains at least two silicon atom-bonded hydrogen atoms per molecule, in an amount such that the number of silicon atom-bonded hydrogen atoms per silicon atom-bonded alkenyl groups on components A, B, C and D is from 0.5 to 5.0, a hydrosilylation catalyst in an amount of from 0.5 to 1,000 ppm with respect to the combined weight of components A to E, and from 0 to 1 part by weight of a filler having an average particle size, measured as described in the description, of not more than 1 μm; which composition has a viscosity at 23°C of at least 100 Pa-s and less than 300 Pa·s. 100 parts by weight of a diorganopolysiloxane has an average degree of polymerization of at least 300 and less than 3,000 and contains at least two silicon atom-bonded alkenyl groups per molecule and has a viscosity at 23°C of from 2 to 200 Pa·s, from 10 to 100 parts by weight of a diorganopolysiloxane which has an average degree of polymerization of less than 300 and contains at least two silicon atom-bonded alkenyl groups per molecule and has a viscosity at 23°C of from 20 to 2,000 mPa·s, from 10 to 200 parts by weight of a diorganopolysiloxane which has an average degree of polymerization of 3,000 to 30,000, contains at least two silicon atom-bonded alkenyl groups per molecule and is gum-like at room temperature, from 5.0 to 20 parts by weight of an organopolysiloxane which consists of units selected from the group consisting of R 3 SiO 1/2 units (M units), SiO 4/2 units (Q units), R 2 SiO 2/2 units (D units) and RSiO 3/2 units (T units), contains M units and Q units as essential constituent units, has a combined amount of M units and Q units that is at least 80 mol % of all constituent units, and has a (number of moles of M units) / (number of moles of Q units) ratio in the range of 0.5 to 1.5 wherein R is a monovalent hydrocarbon group of 1 to 6 carbon atoms, and at least two R groups per molecule are alkenyl groups, an organohydrogenpolysiloxane which contains at least two silicon atom-bonded hydrogen atoms per molecule, in an amount such that the number of silicon atom-bonded hydrogen atoms per silicon atom-bonded alkenyl groups on components A, B, C and D is from 0.5 to 5.0, a hydrosilylation catalyst in an amount of from 0.5 to 1,000 ppm with respect to the combined weight of components A to E, and from 0 to 1 part by weight of a filler having an average particle size, measured as described in the description, of not more than 1 μm; which composition has a viscosity at 23°C of at least 100 Pa-s and less than 300 Pa·s.