Priority research needs determined by the Agency for Toxic Substances and Disease Registry (ATSDR) for the agencies top-ranked hazardous substances are being filled via regulatory mechanisms, private sector voluntarism, and university-based research. To date, 17 studies have been completed, 12 are ongoing, and 12 are currently planned. Under the direction of the Substance-Specific Applied Research Program (SSARP), ATSDR-supported research has filled research needs that significantly improved the information base available for making appropriate public health decisions. With the knowledge and understanding gained from this research, health professionals are better able to identify and interdict significant exposure and mitigate toxicity when exposure occurs. Thus, the SSARP has played, and continues to play, a vital role in contributing towards improving ATSDR's efforts to meet its mission and goals in environmental public health. In addition to addressing research needs of interest to ATSDR, findings from the program have contributed to the overall scientific knowledge about the effects of toxic substances in the environment.