AIM: To determine the plasma carnitine ester profile in adult patients with ulcerative culitis (UC) and compared with healthy control subjects.METHOD: Using ESI triple quadrupole tandem mass spectrometry, the carnitine ester profile was measured in 44 patients with UC and 44 age- and sex-matched healthy controls.RESULTS: There was no significant difference in the fasting free carnitine level between the patients with UC and the healthy controls. The fasting propionyl(0.331 ±0.019 vs0.392 ± 0.017 μmol/L), butyryl(0.219 ± 0.014 vs 0.265± 0.012), and isovalerylcarnitine (0.111 ± 0.008 vs 0.134± 0.008) levels were decreased in the UC patients. By contrast, the level of octanoyl- (0.147 ± 0.009 vs 0.114 ± 0.008),decanoyl- (0.180 ± 0.012 vs 0.137 ± 0.008), myristoyl(0.048 ± 0.003 vs 0.039 ± 0.003), palmitoyl- (0.128 ± 0.006vs 0.109 ± 0.004), palmitoleyl- (0.042±0.003vs 0.031 ± 0.002) and oleylcarnitine (0.183 ± 0.007vs 0.163 ± 0.007; P ＜ 0.05 in all comparisons) were increased in the patients with UC.CONCLUSION: Our data suggest selective involvement of the carnitine esters in UC patients, probably due to their altered metabolism.