The use of advocacy advertising by corporations and special interest groups attempting to influence social policy has increased dramatically in the past decade. Yet little research has been conducted to gauge the effectiveness of advocacy advertising relative to other forms of mass communication. Conventional wisdom suggests that because advocacy material presented in the form of an advertisement is inherently paid-for communication, it will be less effective than the same information appearing in news columns as a published news release. This study uses a factorial design to examine the impact of format (advertisement versus news article) and source (commercial versus noncommercial) manipulations on the effectiveness of advocacy messages.