PIMCO Corporate & Income Opportunity Fund is a closed-end management investment company. The Company's primary investment objective is to seek high current income, with capital preservation and capital appreciation as secondary objectives. The Fund invests approximately 80% of its total assets in a combination of corporate debt obligations of varying maturities, other corporate income-producing securities, and income-producing securities of non-corporate issuers, such as the United States Government securities, municipal securities, and mortgage-backed and other asset-backed securities issued on a public or private basis. The Fund invests approximately 25% of its total assets in corporate debt obligations and other corporate income-producing securities. Its portfolio includes banks, integrated oil, automotive, financial other, non-captive consumer finance and pipelines. Pacific Investment Management Company LLC serves as the Fund's investment manager.