|Steroids are usually present in blood at low concentrations so methods are needed that provide rapid and reliable analysis with high sensitivity. Traditional methods of analysis, such as immunoassays, can suffer from poor accuracy and reproducibility. This poster presents a liquid chromatography tandem mass spectrometry method for measuring total testosterone in serum. For 0.2 mL of serum an LOQ of 0.01 ng/mL was achieved (<10% RSD) with a linear range exceeding 2 orders of magnitude. Results are consistent for what is required for a clinical assay that measures total testosterone in serum.