Organic fluorochemicals are used in multiple commercial applications including surfactants, lubricants, paints, polishes, food packaging, and fire-retarding foams. Recent scientific findings suggest that several perfluorochemicals (PFCs), a group of organic fluorochemicals, are ubiquitous contaminants in humans and animals worldwide. Furthermore, concern has increased about the toxicity of these compounds. Therefore, monitoring human exposure to PFCs is important. We have developed a high-throughput method for measuring trace levels of 13 PFCs (2 per-fluorosulfonates, 8 perfluorocarboxylates, and 3 perfluorosulfonamides) in serum and milk using an automated solid-phase extraction (SPE) cleanup followed by high-performance liquid chromatography-tandem mass spectrometry. The method is sensitive, with limits of detection between 0.1 and 1 ng in 1 mL of serum or milk, is not labor intensive, involves minimal manual sample preparation, and uses a commercially available automated SPE system. Our method is suitable for large epidemiologic studies to assess exposure to PFCs. We measured the serum levels of these 13 PFCs in 20 adults nonoccupationally exposed to these compounds. Nine of the PFCs were detected in at least 75% of the subjects. Perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS), 2-(N-methylperfluorooctanesulfonamido)acetate (Me-PFOSA-AcOH), perfluorooctanoate (PFOA), and perfluorononanoate (PFNA) were found in all of the samples. The concentration order and measured levels of PFOS, PFOA, Me-PFOSA-AcOH, and PFHxS compared well with human serum levels previously reported. Although no human data are available for the perfluorocarboxylates (except PFOA), the high frequency of detection of PFNA and other carboxylates in our study suggests that human exposure to long-alkyl-chain perfluorocarboxylates may be widespread. We also found PFOS in the serum and milk of rats administered PFOS by gavage, but not in the milk of rats not dosed with PFOS. Furthermore, we did not detect most PFCs in two human milk samples. These findings suggest that PFCs may not be as prevalent in human milk as they are in serum. Additional studies are needed to determine whether environmental exposure to PFCs can result in PFCs partitioning into milk. Large epidemiological studies to determine the levels of PFCs among the U.S. general population are warranted.