The determination of HBsAg in 3,404 pregnant women showed 84 positive cases (2.46%), which is above the average for the Spanish population. Notable risk factors were prior liver diseases, sexual promiscuity and spouse with liver disease. Other common, but less significant factors, were histories of transfusion or drug addiction. A very high proportion of the pregnant women were of the Gypsy race (12.1%), and these women showed a statistically higher (p less than 0.001) rate of chronic HBV infection (8.4%) than non-Gypsy population (1.4%). The Gypsy population showed a lower presence of known risk factors but a higher positivity for the e antigen. Our findings suggest that there is a higher prevalence of chronic HBV infection in pregnant Gypsy women and that the infection shows particular epidemiologic features.