Product Liability Risk Retention Act of 1981 - Defines "risk retention group" to mean any corporation or insurance company formed under State law which: (1) is organized for the primary purpose of assuming and spreading product liability or completed operations liability risk exposure; (2) is chartered as an insurance company under State law; (3) does not exclude members for competitive advantage; and (4) consists of members whose principal activity is the manufacture, design, distribution, packaging, or sale of a product.

Defines "purchasing group" to mean any group of persons which has as one of its purposes the purchase of product liability or completed operations insurance on a group basis.

Exempts risk retention groups and purchasing groups from State laws which prohibit, regulate, or otherwise discriminate against such groups.

Enumerates requirements which a State may impose on a risk retention group, including compliance with unfair claims settlement practices laws, payment of taxes, and reporting requirements.

Authorizes a State to license an agent or broker for a purchasing group.

Stipulates that the ownership interests of members in a risk retention group shall not be considered securities or an investment company for purposes of the Federal securities laws or State blue sky laws.