The majority of what is known of the experience of dental caries among adults is from cross-sectional studies, and there are surprisingly few population-level longitudinal studies of dental caries among adults. Dental examinations were conducted at age 26 and again at age 32 among participants in a longstanding prospective study of a birth cohort born in Dunedin (New Zealand) in 1972/1973. Some 901 individuals (88.8%) were dentally examined at both ages. The mean number of remaining teeth and tooth surfaces fell between 26 and 32, reflecting ongoing tooth loss. The overall prevalence of caries rose from 94.9 to 96.8%, while there were greater increases in the proportion with caries-associated tooth loss (from 10.8 to 22.8%). Caries experience was greatest in the molar teeth and upper premolars, and was lowest in the lower anterior teeth. The mean crude caries increment (CCI) was 5.0 surfaces (SD 6.6); 681 (75.5%) experienced 1+ CCI, and the mean CCI among those individuals was 6.6 surfaces (SD 6.9). Substantial dental caries and tooth loss experience occur as people move from the third into the fourth decade of life.