The advances in agricultural biotechnology have brought opportunities and challenges to the agricultural input industries including the seed sector over the last few decades. The U.S. seed market has experienced major structural adjustments during this period. Since 1996 the rapid adoption of biotechnology in U.S. agriculture has been associated with mergers and acquisitions, leading to a more concentrated seed/biotech industry. It raises questions about the possible exercise of market power in the U.S. biotech seed industry. Will an integrated biotech seed company differ from an independent one in choosing the line of seed products? How do U.S. farmers evaluate different types of corn seeds? And how are the welfare gains from technological improvement distributed among market participants? This dissertation tried to answer these questions by investigating the product line choices of seed companies under imperfect competition and farmers' adoption of conventional and genetically modified (GM) seeds in the U.S. corn seed market during 2000-2007. In Chapter 2, I examine seed firms' product choices by considering concentration in the upstream biotech market, geographical competition, firm and market characteristics, and technological advancement, by using a system dynamic panel data model. I find that market competition has discrepant impacts on the product choices of biotech firms and independent companies. Firms' willingness to carry more varieties also differs by their market shares. In Chapter 3, I construct a multiple discrete choice model with random coefficients to estimate farmers' demand. I further impose a flexible correlation structure among products' observable characteristics, and panel effects on individuals' seed choices. I use the simulated Generalized Method of Moments for estimation. Results indicate that farmers' preferences are shifted away from conventional and single traited seeds to newly-introduced multiple traited ones. Their preferences could also become unstable by technology development. In Chapter 4, I investigate the welfare distribution of biotechnology advances among market participants and the welfare changes when biotech firms specialize in GM seeds and independent firms specialize in conventional seeds. I find that the benefits of biotechnology advances are received mostly by medium-to-large farms and a few biotech companies. Biotech firms also benefit from market segmentation.