Abstract: A rubber composition is disclosed which contains, as a rubber component, 20-100% by weight of (A) polybutadiene polymerized by using a lithium initiator and 80 to 0% by weight of (B) another rubber component. The polybutadiene has the following physical properties (i)-(v):(i) The molecular weight distribution of Mw/Mn is 1.4 to 3.0 in which Mw and Mn are a weight average molecular weight and a number average molecular weight, respectively;(ii) A polymer component having the molecular weight being not more than 10.sup.5 when calculated as polystyrene is from 7 to 25%;(iii) The content of bound vinyl groups is from 10 to 25%;(iv) The content of tin atoms bonded to the polymer by tin-carbon bonds is not less than 50 ppm;(v) Mooney viscosity (ML.sub.1+4, 100.degree. C.) is from 20 to 70.