The Agency has addressed the carcinogenic potency of mixtures of materials in the ambient air which is a critical step towards characterizing the exposure of humans to a complex environment. The Integrated Air Cancer Project was found to be scientifically well-founded. The project represents a logical and appropriately innovative approach that can achieve its long-range goals of addressing these complex environmental health issues. In addition, the project effectively exploits some of the research tools and results developed in the past decade and presents an example of effective multi-laboratory research management within the Agency.