The aim of this study was to assess the relationship between Helicobacter pylori (Hp) infection, serum thyroid hormone levels and certain cardiovascular risk factors in normal volunteers. In 110 blood donors (85 men, 25 women, aged 35.6 +/- 9.76) the serum levels of IgG antibodies against Hp were estimated using a sensitive immunoassay. Serum estimation of T3, T4, TSH, FT3, FT4, thyroid (microsomial) autoantibodies, C-Reactive-Protein, a1-acid-glycoprotein, vitamin B12, folic acid, cholesterol, triglycerides, total lipids, HDL, LDL, and antibodies against hepatitis A, was also carried-out. In all subjects a number of clinicoepidemiological parameters including body mass index, smoking habits, educational level, number of siblings and presence of symptoms from the digestive system were carefully recorded. Statistical analyses were performed using the SPSS statistical package. Helicobacter pylori infection was found in 54 subjects (49.1%). On univariate analysis, significant differences between subjects positive and negative for Helicobacter pylori infection were found for FreeT3 (3.11 +/- 0.5 pmol/ vs. 3.42 +/- 0.8 pmol/l, P=0.025), FreeT4 (1.04 +/- 0.2 ng/dl vs. 1.17 +/- 0.3 ng/dl, P=0.025), and thyroid autoanti bodies (23.65 +/- 24 vs. 14.97 +/- 8, P=0.018). Significant differences were also found for Cholesterol (207.8 +/- 39 mg/dl vs. 193.3 +/- 40 md/dl, P=0.05), LDL (133.2 +/- 32 mg/dl vs. 119.6 +/- 40 mg/dl, P=0.05) and folic acid (7.66 +/- 3.7 ng/ml vs. 6.39 +/- 2.5 ng/ml, P=0.038). A significantly positive correlation of Hp infection with age and number of siblings and a negative one with educational level were noticed. No differences concerning the levels of acute phase proteins, vitamin B12, antibodies against hepatitis A, body mass index, and smoking habits were found. On logistic regression analysis, significant differences remained only for thyroid autoantibodies (Odds ratio for titer ?30: 7.8, P=0.012), age (Odds Ratio for those aged >40 years vs those aged <40 years: 3.8, P=0.022) and educational level (Odds ratio for elementary 8.7 and moderate 5.1 vs higher education, P=0.003 and P=0.011 respectively). It is concluded that a relationship exist between Hp infection and the presence of high titers of thyroid autoantibodies in blood donors. There are no indications of the existence of a relationship between Hp infection with thyroid hormone levels, lipid concentrations and other cardiovascular risk factors.