We study an environment with short-sale constraints and heterogeneous beliefs among outsiders and between insiders and outsiders. Firm insiders choose between equity, debt, and convertible debt to raise external financing. We analyze two settings: one in which heterogeneous beliefs is the only market imperfection and another in which there are significant security issue and financial distress costs. Our model generates a pecking order of external financing different from asymmetric information models, and new predictions for capital structure, sequential tranching of securities, the price impact of security issues, and long-run stock returns. We also provide a new rationale for convertible debt issuance.