This paper examines the role of patents in the development and use of two platform technologies for plant biotechnology - plant transformation techniques and structural genomics. We find that patents were important in inducing private firms to develop these platform technologies. There development led to the commercialization of more GM varieties, more rapidly than would have been the case otherwise. We did identify a number of examples of GM varieties that were slowed down by the patents on tools. However, our preliminary assessment of the evidence suggests that the benefits from patents on tools outweigh the costs.