C-reactive protein (CRP) is a biomarker for inflammation due to infections or other medical conditions (e.g. rheumatoid arthritis or lupus). Because persistent low levels of inflammation can also be associated with cardiovascular disease, high-sensitivity CRP (hs-CRP) assays that can detect low levels of CRP in serum are used to predict risk of heart disease combined with other mitigating factors. In a healthy individual, CRP is found at a level less than 1 milligram per liter (mg/L) in serum. Recent evidence suggests that a CRP level between 1 mg/L and 3 mg/L indicates a moderate risk of cardiovascular disease while a level greater than 3 mg/L predicts a high risk. The NIST team produced the certified reference material of pure CRP for the intended purpose of calibrating diagnostic tools and procedures that measure these low levels of CRP with greater accuracy, precision and traceability to the International System of Units (SI). A unit of the SRM contains 3 vials, each with 1 mL of a solution of recombinant CRP in aqueous buffer containing 20 mmol/L TRIS-HCl (pH 7.5), 140 mmol/L NaCl, 2 mmol/L CaCl2 and a volume fraction of 0.05 % NaN3. A certified concentration value for CRP is reported along with reference density, relative average mass and concentration values (expressed in terms of grams per liter). SRM 2924 was certified for concentration by amino acid analysis involving isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS). This advanced measurement method was optimized and rigorously tested against an existing higher-concentration certified reference material for CRP from the National Metrology Institute of Japan. Stability of the SRM was also carefully assessed through chromatographic and mass spectrometric techniques. SRM 2924 was developed by NIST to meet the needs of the in-vitro diagnostic and research communities for a “higher order” reference material to obtain traceability to SI units. The SRM is stored and shipped frozen and must be thawed at room temperature before use.