Antitakeover amendments (shark repellents) restrict the transfer of corporate control. On average, the public announcement of antitakeover amendments by 600 firms in the period 1979–1985 has an insignificant effect on the value of announcing firms' shares. However, different types of amendments have varying effects. Non-fair-price amendments have an average significant negative effect of 2.95% on share prices, while fair-price amendments have an insignificant effect. The more harmful amendments have larger insider holdings and lower institutional holdings, suggesting a partial explanation of why shareholders approve these amendments.