This report on interstate child support cases focuses on child support enforcement problems that occur when absent parents live in states other than those in which their children reside. Findings indicate that Office of Child Support Enforcement (OCSE) and state caseload and collection data are of questionable reliability and provide limited information about interstate child support. OCSE data cannot be used to determine the relative size of states' interstate versus total caseload. OCSE data indicate that total interstate collections for fiscal year 1987 were about seven percent of total child support collections. Available caseload data show that over half of all interstate case activity is taking place in seven states. States estimate that case processing takes longer and is less successful for interstate cases sent to other states than for in-state cases. States use varying laws and processes for enforcing interstate child support. New case processing methods are tested in interstate demonstration projects. Insufficient staff, lack of automation, and differences in states' policies, procedures, and laws are identified as barriers to effective interstate enforcement. Officials cite a variety of actions, such as standardizing policies and procedures and establishing performance standards, that could improve interstate enforcement. The study instrument is appended. (RH)