Recent mergers in the seed industry have led to concerns about market concentration and its potential effects on prices, product choice, and innovation. This study provides new and detailed empirical evidence on the degree of market concentration in seed and GM technology across a broad range of crops and countries, and analyses the causes and potential effects of concentration. It also explains how competition authorities have responded to mergers, and suggests policy options to help safeguard and stimulate competition and innovation in plant breeding by avoiding unnecessary regulatory barriers, by facilitating access to genetic resources and intellectual property, as well as by stimulating public and private R&D. As this study shows, policy makers have several levers besides competition policy to ensure an innovative and competitive seed industry.