OBJECTIVE: To determine if the serum phospholipid fatty acid pattern in patients with cystic fibrosis (CF) was related to the major cystic fibrosis transmembrane conductance regulator gene mutations. METHODS: Patients with CF (n = 110) aged 3 months to 56 years were studied. Serum samples were analyzed for phospholipid fatty acid with gas-liquid chromatography, and cystic fibrosis transmembrane conductance regulator mutations were determined with standard methods. RESULTS: Patients with CF had significantly lower molar percentages of linoleic acid and docosahexaenoic acid in the serum phospholipid than healthy controls (mean +/- standard deviation, 20.3 +/- 4.5 and 2.6 +/- 0.9 vs 22.4 +/- 2.2 and 3.1 +/- 0.7, respectively; P