Controls on the supply and promotion of complementary medicines in Australia are weak. We used weight-loss products as an example to compare the regulation in Australia of listed complementary medicines and registered pharmaceutical products. Complementary medicines are listed without evaluation for efficacy, while conventional pharmaceutical products are registered after evaluation for quality, safety and efficacy. From 1996 to 2006, over 1000 "weight-loss" products were listed on the Australian Register of Therapeutic Goods; most contained multiple unevaluated ingredients (herbs, vitamins, minerals) of dubious efficacy. Over the same period, 10 conventional medicines were registered; each contained one evaluated ingredient of proven efficacy. The number of listed weight-loss products (and complaints about their promotion) is increasing. These appear to be a direct consequence of the decision not to evaluate listed products for efficacy and the lower fees for listing a product, compared with registration. Complaint procedures (now overloaded) are no substitute for adequate regulation at the time of market entry. Regulatory reform of listed and homoeopathic products is required.