A tender offer is a proposal to buy shares of stock from the stockholders for cash or some type of corporate security of the acquiring company.

Since the mid-1960s, cash tender offers for corporate takeovers have become favored over the traditional alternative, the proxy campaign.

A proxy campaign is an attempt to obtain the votes of enough shareholders to gain control of the corporation's board of directors.

Because of abuses with cash tender offers, Congress passed the Williams Act in 1968, whose purpose is to require full and fair disclosure for the benefit of stockholders, while at the same time providing the offeror and management equal opportunity to fairly present their cases.

In recent years, as complicated forms of derivatives bearing upon but not actually constituting corporate stock have become common, interpretation of the Williams Act has become tricky.