Ion chromatography with suppressed conductivity was used to develop the California Department of Health Services trace concentration method for perchlorate analysis. This article describes an ion chromatography method to analyze trace concentrations of perchlorate in drinking water. Perchlorate was separated from anions commonly found in groundwater and surface water by elution through an AS5 anion exchange column with 120 mmol/L sodium hydroxide + 2 mmol/L ρ‐cyanophenol. Analytes were measured by conductometric detection using signals enhanced by chemical suppression of the conductance from the eluent. A 740‐μL sample injection provided the sample mass necessary to achieve a perchlorate method detection limit of ≤ 1 μg/L and a working range of 2.5–100 μg/L, without sample preconcentration. Interference studies showed that 5.0 μg/L of perchlorate could be measured in the presence of 1,000 mg/L of bicarbonate, chloride, or sulfate. The method was successfully used to survey drinking water wells in California considered vulnerable to perchlorate contamination.