<p>A random copolymer of a C4 to C12 alpha -olefin with an aromatic vinyl monomer, wherein the alpha -olefin content is 50 to 98 mole % and the softening point is 40 to 150 DEG C, is useful as a hot-melt adhesive and excellent in adhesion, processability and environmental aging resistance such as thermal aging resistance. The copolymer can be used as a hot-melt adhesive or a heat sealant when combined with 70 to 10 wt% of a tackifier.</p>