Trichloroethylene (TCE), a large part of the toxic spill in Endicott, NY, has harmful effects on human health. The major exposure pathway for Endicott residents is inhalation of the TCE vapor that is percolating up from an underground plume. Past exposure routes also included ingestion through drinking water. Has this exposure to TCE negatively affected the health of Endicott residents, or even shortened their lives? The answer to this question seems to be a resounding “maybe.” While the methodologies used to perform risk assessment are relatively straightforward, the case and cohort studies used to develop a risk assessment for TCE are subject to interpretation. The difference in interpretation has provided a scientific basis for developing guideline TCE concentrations requiring action or mitigation that differ by two orders of magnitude.