The provision of accurate, in-depth data on substance abuse trends and service needs has become increasingly important in light of the growing wave of substance abuse in South Africa and particularly in the Western Cape Province. This article describes the design and implementation of an electronic substance abuse surveillance system (SASS) between 2007 and 2009. The function of this system is to gather data on substance use, associated problems, service needs and services received on all clients presenting for generic social welfare services at the 16 district social service offices in the Western Cape. This article describes key features of SASS, examines the strengths of this system, reviews the process of implementing SASS and describes major challenges to the effective implementation and use of the system. Major challenges include limited infrastructure, inadequacies in staff capacity and lack of organizational support for the system. Recommendations for addressing these challenges and improving the use of this surveillance system are provided. (Contains 1 table and 1 figure.)