This report summarizes research involving the determination of parameters causing water damage to asphalt concrete. The study was a cooperative effort between the Federal Highway Administration (FHWA) and NMERI. Bituminous mixtures with a history of water susceptibility were fabricated by FHWA. Compacted mixtures were evaluated for moisture damage at FHWA, then shipped to NMERI for chemical analysis of the binders. Extracted binders were analyzed by a modified Clay-Gel procedure and infrared spectroscopy to determine whether differences between moisture conditioned and control asphalts could be measured. An Index of Relative Severity (water damage) has been defined from analysis of the data. Changes in certain asphalt chemical constituents may relate to retained strength for mixtures without antistripping additives. Potential moisture damage is predicted equally with a least two mechanical tests used for mixtures antistripping compounds. Keywords: Clay-Gel compositional analysis, asphaltenes, saturates, aromatics, polars, asphalt generic composition, asphalt functional group concentrations, ketones, sulfoxides, carboxylic acids, IR spectroscopy, Lottman procedure, Immersion-Compression, percent retained strength, antistripping additives or agents, moisture-damage severity, and degree of relative severity.