Describing a bond with a medium or high rating. Bonds rated Baa3 by Moody's or BBB- by S&P or Fitch. Investment-grade bonds are considered sufficiently low-risk that the law allows banks to invest in them. In addition to being low-risk, investment-grade bonds are low-return, greatly reducing the cost on the issuer. Most American Treasury and municipal bonds are investment-grade. See also: Junk, High-Rating.