Increasing reliance on biomarkers in drug development programs demands that assays for measuring those biomarkers have acceptable analytic performance. Biomarkers are used in preclinical studies to confirm targets and elucidate mechanisms of action of novel therapeutic agents. In that context biomarker assays must be sufficiently precise and reproducible that biomarker modulation can be detected reliably amid noise introduced by technical and specimen pre-analytic factors. For clinical trials in which biomarkers are used for patient selection or monitoring for therapeutic effects or toxicity, it is important that biomarker assays deliver accurate data that will confidently inform decisions regarding eligibility and benefit and safety of treatment for individual patients. Metrics and study design considerations for assessment of assay analytic performance are discussed in the context of several examples spanning biomarker applications in different disease settings and therapeutic development stages.