Through a series of scientific presentations, workshop participants explored three major critical loads research topics: (1) the strengths and weaknesses of simple mass balance and dynamic models for calculating critical loads, (2) the application of empirical methods for estimating critical loads, and (3) the state of air, water, soil, and forest monitoring data to support critical loads development. Based on the scientific presentations, a research and monitoring agenda for advancing the science of critical loads emerged. The agenda encompasses atmospheric emissions and deposition, soils, surface waters, biological effects, and critical loads modeling. It emphasizes the need for improved nitrogen emission inventories and total deposition estimates for sulfur and nitrogen, hybrid approaches that combine models with empirical observations, and an improved understanding of relationships between chemical criteria and biological responses in aquatic and terrestrial ecosystems.