A heat conductive silicone grease composition comprising: 5 to 99 parts by weight of organopolysiloxane represented by the general formula: wherein each R 1 independently is a substituted or unsubstituted C 1 -C 18 monovalent hydrocarbon group, each R 2 independently is alkyl, alkoxyalkyl, alkenyl or acyl group, a is an integer of 5 to 100 and b is an integer of 1 to 3, and having a kinematic viscosity at 25°C determined in accordance with the method of the description of 10 to 10,000 mm 2 /s, 1 to 95 parts by weight of organopolysiloxane represented by the average compositional formula: R 3 c SiO (4-c)/2 wherein each R 3 independently is a substituted or unsubstituted C 1 -C 18 monovalent hydrocarbon group and c is a number of 1.8 to 2.2, and having a kinematic viscosity at 25°C determined in accordance with the method of the description of 10 to 100,000 mm 2 /s, the total amount of components and being 100 parts by weight, spherical aluminum oxide powder having an average sphericity of at least 0.8, a count of up to 30 surface hydroxyl groups/nm 2, and an average particle size of 3 to 20 μm, the content of coarse particles with a size of from 25 to 45 μm in the laser diffraction-type particle size distribution being up to 0.2% by weight based on the overall powder, and spherical and/or irregular zinc oxide powder having an average particle size of 0.01 μm to less than 3 μm, the content of coarse particles with a size of from 25 to 45 μm in the laser diffraction-type particle size distribution being up to 0.2% by weight based on the overall powder, components and being blended in a weight ratio of from 5:5 to 9.5:0.5, the total amount of components and being 65 to 83% by volume of the overall composition, the composition having a thermal conductivity of 2 W/m·K to less than 5.5 W/m·K as measured by the hot disk method according to ISO 22007-2, and a viscosity at 25°C of 5 to 800 Pa·s as measured by a spiral viscometer at rotational speed 10 rpm. 5 to 99 parts by weight of organopolysiloxane represented by the general formula: wherein each R 1 independently is a substituted or unsubstituted C 1 -C 18 monovalent hydrocarbon group, each R 2 independently is alkyl, alkoxyalkyl, alkenyl or acyl group, a is an integer of 5 to 100 and b is an integer of 1 to 3, and having a kinematic viscosity at 25°C determined in accordance with the method of the description of 10 to 10,000 mm 2 /s, 1 to 95 parts by weight of organopolysiloxane represented by the average compositional formula: R 3 c SiO (4-c)/2 wherein each R 3 independently is a substituted or unsubstituted C 1 -C 18 monovalent hydrocarbon group and c is a number of 1.8 to 2.2, and having a kinematic viscosity at 25°C determined in accordance with the method of the description of 10 to 100,000 mm 2 /s, the total amount of components and being 100 parts by weight, spherical aluminum oxide powder having an average sphericity of at least 0.8, a count of up to 30 surface hydroxyl groups/nm 2, and an average particle size of 3 to 20 μm, the content of coarse particles with a size of from 25 to 45 μm in the laser diffraction-type particle size distribution being up to 0.2% by weight based on the overall powder, and spherical and/or irregular zinc oxide powder having an average particle size of 0.01 μm to less than 3 μm, the content of coarse particles with a size of from 25 to 45 μm in the laser diffraction-type particle size distribution being up to 0.2% by weight based on the overall powder, components and being blended in a weight ratio of from 5:5 to 9.5:0.5, the total amount of components and being 65 to 83% by volume of the overall composition, the composition having a thermal conductivity of 2 W/m·K to less than 5.5 W/m·K as measured by the hot disk method according to ISO 22007-2, and a viscosity at 25°C of 5 to 800 Pa·s as measured by a spiral viscometer at rotational speed 10 rpm.