This short course provides the tools to determine if you really have metals contamination in ground water or surface water at your site. Trace-element adsorption on specific suspended particulates (e.g., clays, iron oxides) is well known. Under oxidizing, circumneutral pH conditions, this adsorption affinity typically yields strong correlations between trace elements vs. aluminum or iron. These relationships are visualized with scatter plots of trace vs. major element concentrations. Consistent elemental ratios are observed for uncontaminated samples; contaminated samples are identified by anomalously high elemental ratios. Other important factors are pH, redox effects, aqueous complexation, and salinity gradients. In contrast to purely statistical approaches, geochemical evaluations reduce false-positive declarations of contamination, do not require statistically valid background data sets, and provide mechanistic explanations for elevated concentrations. Insightful case studies are presented from numerous sites across the U.S. This course is recommended for regulators as well as consultants and site managers.