Transgenic cultivars are obtained by the introduction of genes from different species directly into the plant genome. On the one hand these cultivars represent a major advance in genetic improvement, and on the other can contribute to a real monopoly in the seed market owing to the existing legal systems of protection. Of great interest in respect of the development of transgenic cultivars is the process of patenting biotechnology products under Brazilian Industrial Property Law. Theoretically, the patent holder of a transgenic gene could control all cultivars into which the gene is introduced. One way of preventing this has been the institution in Brazil of the Plant Cultivar Protection Act. Both these bills give the patent holders and the holders of the cultivars the right to receive royalties on the use and/or commercialization of patented or protected material. Therefore, transgenic crops can, in a sense, be covered by two laws, which has sometimes led to conflicts. However, only the process and the biotechnology products involved in the production of genetically modified organisms and not the transgenic cultivar obtained can be patented. The cultivar itself is only protected under the Plant Cultivar Protection Act after issuance of a conclusive technical opinion by CTNBio (the Brazilian National Technical Commission on Biosafety). After that, seed can be marketed in the country, although it must be registered in the National Register of Plant Cultivars. Details are included of certified conventional and transgenic cultivars of a large range of Brazilian crops, and of the effect of royalties on the final product cost of protected cultivars.