There is a lack of awareness among Australian and New Zealand medical practitioners about how competition law applies to them. In this article, basic legal issues relating to interaction between medical practitioners (which all medical practitioners should be aware of) are discussed. The New Zealand Ophthalmologists Case and some relevant Australian and United States cases are analysed. Three key areas of competition law (of relevance to medical practitioners) are identified as being important and relevant. In conclusion, medical practitioners must be able to distinguish between legal and illegal activities; and guidelines outlined in this paper provide some clarification.