OBJECTIVES: HIV/AIDS surveillance methods are under revision as the diversity of HIV epidemics is becoming more apparent. The so called "2nd generation surveillance (SGS) systems" aim to enhance surveillance by broadening the range of indicators to prevalence, behaviors and correlates, for a better understanding and a more complete and timely awareness of evolving epidemics. METHODS: Concepts of HIV SGS are reviewed with a special focus on injecting drug users, a major at-risk and hard to reach group in Europe, a region with mainly low or concentrated epidemics. RESULTS: The scope of HIV/AIDS surveillance needs to be broadened following principles of SGS. Specifically for IDUs we propose including hepatitis C data as indicator for injecting risk in routine systems like those monitoring sexually transmitted infections and information on knowledge and attitudes as potential major determinants of risk behavior. CONCLUSIONS: The suggested approach should lead to more complete and timely information for public health interventions, however there is a clear need for comparative validation studies to assess the validity, reliability and cost-effectiveness of traditional and enhanced HIV/AIDS surveillance systems.