A liquid chromatography tandem mass spectrometric (LC-MS/MS) method with postcolumn addition of acetonitrile for the determination of ethyl glucuronide (EtG) and ethyl sulfate (EtS) in meconium was developed and validated using pentadeuterated EtG and pentadeuterated EtS as internal standards. The analytes were extracted from the matrix by acetonitrile, concentrated by solid phase extraction, separated using a reversed-phase chromatographic column, and quantified within 9 minutes. Lower limits of quantification were 5 and 1 ng/g meconium for EtG and EtS, respectively. Calibration curves were linear from lower limits of quantifications to 500 ng/g, with a minimum r > 0.999. At 3 concentrations spanning the linear dynamic range of the assay, mean recoveries ranged between 78.7% and 96.8% for EtG and between 72.1% and 95.6% for EtS. Inaccuracy was better than 8.1%, with intra-assay and interassay imprecision better than 7.2% and 10.5%, respectively. Matrix effects (ion suppression/enhancement) were found to be negligible. The analytes of interest were stable at room temperature, at 4 degrees C, when exposed to 3 freeze-thaw cycles, and when stored at -20 degrees C for up to 6 months. This sensitive and specific method was used to assess the presence of these alcohol biomarkers in meconium samples from 2 different city cohorts.