AIM: To study the prevalence and clinical significance of hyperhomocysteinemia (hHcys), an independent factor for arterial and venous thrombosis, in a group of patients with ulcerative colitis (UC).METHODS: Fasting homocysteine (Hcys), folate, and vitamin B12 serum levels were measured in 40 UC patients and 50 healthy controls. Clinical data regarding UC were gathered.RESULTS: Median serum Hcys levels in UC patients were similar to those in controls (12.26 μmol/L vs 12.32 μmol/L), but the prevalence of hHcys was higher in UC patients than in controls (30% vs 10%, P= 0.028). UC significantly increased the risk of hHcys (adjusted odds ratio: 4.125;95% CI: 1.26-13.44). Multivariate regression analysis showed that male sex, folate and vitamin B12 deficiency or lower serum values were significant independent predictors of higher Hcys levels in UC patients (r2 = 0.4; P＜0.001).CONCLUSION: hHcys is common in UC patients and it is related to folate and vitamin B12 deficiency or lower serum values. It would be reasonable for patients with UC to receive folate and vitamin B complex supplements as a prophylactic measure.