OBJECTIVE To obtain regional epidemiological data on hepatitis delta virus (HDV, a defective virus) infections, the incidence of anti-HDV positivity and the associated risk factors in asymptomatic hepatitis B virus surface antigen (HBsAg) carriers and in patients with chronic active hepatitis B. METHODS The study took place at Dicle University Hospital (Diyarbakir, Southeast of Turkey) between January 2002 and July 2004. Anti-HDV screening was performed in asymptomatic hepatitis B carriers (N=889) and in patients with chronic active hepatitis B infection (N=120). We explored the association between anti-HDV positivity and asymptomatic hepatitis B carrier status, presence of active hepatitis B, age, gender, the durations of HBsAg positivity and hepatitis B e antigen (HBeAg) positivity. RESULTS In 6% of asymptomatic hepatitis B carriers (53/889) and in 27.5% of patients with chronic active hepatitis B (33/120) anti-HDV was positive. The incidence of anti-HDV positivity was significantly higher in patients with chronic active hepatitis B compared with asymptomatic carriers (p<0.001). A significant association between the duration of HBsAg carrier status (3.2 +/- 1.4 years) and anti-HDV positivity was also found (p<0.001). Age, gender, and HBeAg positivity were not significantly associated with anti-HDV positivity (p>0.05). CONCLUSIONS Anti-HDV positivity was significantly more common in patients with chronic hepatitis B compared with asymptomatic hepatitis B virus (HBV) carriers in a region with a high prevalence of HBV infection. We found a significant relationship between the duration of HBsAg carrier status and anti-HDV positively, however, age, gender, and presence of HBeAg were not significantly associated with the development of anti-HDV positivity.