Ground-water seeps in the Catskill Mountains are important water sources for streams and often have different chemistry than nearby surface water. Many studies have shown correlations between water chemistry and plant species composition in wetlands, but there are no such studies in the Catskill Mountain ground-water seeps. The objective of this study was to identify the chemical and physical environmental variables that most strongly influence plant species composition in seeps. Environmental variables and plant species abundance were measured at 33 seeps. TWo-way INdicator SPecies ANalysis with analysis of variance and Canonical Correspondence Analysis showed that plant species composition is determined primarily by water depth and alkalinity/acidity complex gradients. Growing season changes in water chemistry were not shown to influence the plant community.