There are few data on the incidence of dental caries in Lithuanian adults. The aim of the present study was to describe caries and treatment experience among 35-44 and 65-74-year-olds, and to relate this to certain selected independent variables (gender, urban/rural residence, drinking water fluoride levels, and years of education). A total of 680 subjects selected based on a stratified random sampling procedure (response rate 52%) were examined by one examiner. Dental caries was recorded as DMFT following the WHO recommendations. The results showed that the median DMFT scores were 18 for the 35-44-year-olds (n = 380) with median DT = 2, MT = 5, FT = 7. For the 65-74-year-olds (n = 300) the median DMFT was 24, with DT = 1, MT = 18, FT = 2, respectively. One percent of all 35 year-olds and 11% of 65-74-year-olds were edentulous. In the younger age group, statistically significant differences in the DMFT scores were related to gender, urbanization and drinking water fluoride levels. Participants from areas with high fluoride content in the drinking water (> 1.5 ppm F/1) had lower DT, MT, and FT values. Females and participants from urban areas had higher numbers of FT. Participants with more years of education had lower DT, MT, and higher FT values. In the elderly, DMFT scores were related to water fluoride levels and years of education. Individuals with more years of education had higher numbers of FT and lower MT values in this age group. Poor oral hygiene was associated with high numbers of DT in both age groups. The data indicate that dental caries is widespread among adult Lithuanians.