In response to Congressional requests to analyze proposed federal programs that would provide income-contingent loans (ICLs) to postsecondary students, this report of the Congressional Budget Office examines the fundamental issues in designing such programs. It identifies the key parameters that define an ICL program, discusses the relationships among them, and explores other issues that bear on how an ICL program could be fashioned. Specific questions addressed include whether ICLs should be federally subsidized, whether some borrowers subsidize other borrowers, and if borrowers would alter their behavior in response to the terms of an ICL. Other factors that would affect the terms of an ICL are discussed including cumulative loan amount, length of repayment period, payback rate relative to income, interest rate, and the administrative burden on the borrower. The report also includes a table of the basic types of income-contingent loans. (GLR)