When there is concern about a patient's fat intake or blood lipid levels, tests ordered are usually restricted to cholesterol, triglyceride, HDL, and LDL. Occasionally, a lipoprotein electro-phoresis or lipoprotein-a (Lp-a) are ordered. In addition to those tests listed above, at The Center we routinely measure red blood cell membrane (RBC) fatty acids using modifications of existing procedures. RBC membrane fatty acid analysis is a very difficult procedure to perform and The Center is one of the few clinical institutions in the U.S.A. performing this test. The test is very complex and involves lipid extraction, methylation, separation steps and final analysis by gas chromatography. Plasma fatty acids can also be measured. However, the RBC profile is preferred because RBC fatty acids reveal long-term fatty acid balance in the tissues and is not influenced by recent dietary fat intake.