TraceBase is a data repository and analysis tool for mass-spectrometry data from isotope tracing studies used to quantify metabolism in vivo. Lab members submit peak data exported from El-Maven and processed for natural abundance correction by AccuCor, IsoCor, or Iso-AutoCor along with details about their experiment. TraceBase computes useful metrics such as enrichment, normalized labeling, and estimated FCirc (rate of appearance/disappearance), making it simple to browse, collate, compare, and download the data.