Summary: An audit of the U.S. Customs Service reveals that the agency cannot fully account for tons of illegal drugs and millions of dollars seized from drug dealers, adequately control the use of its operating funds, and ensure that importers are complying with laws to ensure fair trade. During fiscal year 1993, the U.S. Customs Service took several meaningful steps toward addressing recommendations resulting from GAO's audit of the fiscal year 1992 statements. Most importantly, Customs began a program to reliably measure compliance with trade laws; developed a methodology for accurately reporting its $900 million in accounts receivable; and, for the first time, did a nationwide inventory of its seized assets. More substantial improvements, however, will be needed to develop meaningful and reliable financial management information and establish a sound internal control structure. Consequently, GAO is unable to express an opinion on Customs' fiscal year 1993 Principal Financial Statements. This report highlights Customs' serious financial management and control problems and describes the harmful effect of these problems on Customs' ability to carry out its trade and enforcement missions. GAO also describes Customs' efforts to correct the problems and makes recommendations to help Customs resolve these problems and strengthen its financial management operations.