Ukraine has been experiencing epidemic diphtheria since 1991. In efforts to control this epidemic, a mass vaccination campaign was held in April 1995. Persons not vaccinated in the previous 3 years were considered eligible for vaccination with tetanus-diphtheria toxoids (Td). Two cluster sample surveys were conducted to determine vaccination coverage achieved. In the urban and rural survey areas, respectively, 628 and 618 persons 30-49 years of age were interviewed. Fifty-nine percent of urban and 58% of rural participants were eligible for vaccination. During the vaccination campaign, 58% (95% confidence interval [95% CI], 47.1-69.2) of eligible persons received Td in the urban area, compared with 92% (95% CI, 89.2-95.3) in the rural area. Apparent barriers to vaccination included misconceptions about the safety, efficacy, and need for booster doses of Td. Future vaccination campaigns should include targeted information and education messages. Mass vaccination campaigns can be successful in vaccinating large numbers of adults; however, in urban areas, additional efforts may be required to achieve levels of coverage adequate to confer herd immunity and interrupt the diphtheria epidemic.