A pressure sensitive adhesive composition which comprises the following two components: (A) a vinyl polymer having at least one alkenyl group represented by the general formula (1): CH.sub.2.dbd.C(R.sup.1)-- (1) wherein R.sup.1 represents a hydrogen atom or a methyl group; (B) a hydrosilyl group-containing compound is provided. The composition can give cured products having a high gel fraction and can be cured rapidly since the degree of alkenyl group introduction is high.