A bill to amend the Clayton Act to provide for a presumption with respect to the effect of certain acquisitions on competition.

Amends the Clayton Act to establish a presumption that an acquisition or use of stock substantially lessens competition or tends to create a monopoly, if such acquisition or use is likely to substantially foreclose the availability of supply sources or distribution outlets for any person in any line of commerce of the acquiring person or of the person whose stock, share capital, or assets are to be acquired. Permits rebuttal of such presumption by evidence that such acquisition or use would create substantial efficiencies that are likely to benefit consumers.