This paper analyzes the profitability of vertical integration for an upstream monopoly facing a potential competitor. We show that it depends on the technology used by the firm when it integrates. We distinguish two types of technologies: standard technologies, used by nonintegrated firms, and nonstandard technologies, reserved for integrated firms and implying the complete foreclosure of nonintegrated firms. Vertical integration with the adoption of a nonstandard technology dominates vertical integration with the adoption of a standard technology and is profitable, as long as the degree of competition in the downstream industry is sufficiently low. Copyright (c) 2000 Massachusetts Institute of Technology.