Direct to consumer advertising (DTCA) of prescription medicines has generated considerable controversy in both New Zealand and the United States, the only two countries that currently permit promotion ofrestricted medicines. Arguments against DTCA include the effect this may have on doctor-patient relationships, its implications for drug costs, and the extent to which it fully informs potential patients. Conversely, proponents of DTCA claim that it increases knowledge of a variety of common medical conditions, thus fostering earlier diagnosis and better compliance with treatments. However, although arguments for and against DTCA have merit, neither side has supported its position with empirical evidence. In particular, the extent to which DTC promotions communicate effectively and achieve their objective of improving wider consumer knowledge remains unclear. This paper critically evaluates the alleged effects of DTCA and outlines our research agenda, which is designed to bridge current knowledge gaps and provide a more informed basis for public policy decisions.