The National User Resource for Biological Accelerator Mass Spectrometry at Lawrence Livermore National Lab is an NIH supported center with over 30 years of expertise in the development and application of Accelerator Mass Spectrometry (AMS) for biomedical sciences. The User Resource makes cutting edge AMS technology, including a unique parallel accelerator and molecular mass spectrometry (PAMMS) system, available to biomedical researchers. We specialize in ADME, dose-response, mass balance, pharmacokinetic and metabolic pathway analyses, protein and nucleic acid adduct formation, and biomarker identification. Access is free for nearly all academic investigators.