The system behavior of regional models can not be evaluated with existing data bases, such as SURE, OSCAR, or the NTN/NADP, in part because they were not designed with model evaluation in mind. Simultaneous measurements of air quality, precipitation chemistry, and dry deposition, which are necessary for a fully rigorous integrated evaluation, are lacking in present data bases. New, more comprehensive data sets with coincident measurement of the major species are needed. A discussion of data needs for the collection of chemical data as part of the design of a new field study to collect such data is presented. Since a surface network will be the backbone of the data base, the chemical data needs of the surface network receives the most attention. First the species which need to be measured are discussed, and then the spatial and temporal data needs are discussed.