This research, conducted via interviews at 32 biotechnology firms, which provide rare information on actual firm interactions, elucidates the factors that influence the location and growth of the biotechnology sector in a typical American metropolitan area. Results indicate that most of the biotechnology firms within the Cincinnati region are there because of entrepreneurial ties with universities and research hospitals in the area, not because the region has specific advantages for biotechnology firms compared to other metropolitan areas of similar size. The authors find that interfirm linkages range from extremely weak to nonexistent. No specialized labor force exists to support biotechnology firms, nor are there specialized infrastructure and business services. No biotechnology-dedicated government office exists. In summary, the authors see more colocation than interactive clustering of biotechnology firms, implying that economic development efforts to enhance interfirm linkages are likely to be less effective than support for hospital and university research and education.