Although pain during dental treatment has been identified as playing a major role in the onset of dental anxiety and is a major concern of patients when seeking dental care, there have been very few studies of the prevalence of pain during dental treatment and the factors associated with patients' perceptions of pain. This study used data from a longitudinal population-based study to assess the proportion of dental attenders who experienced pain while having dental treatment and the psychological characteristics which predisposed them to experience pain. Of 1422 subjects who completed questionnaires at baseline and five-year follow-up, 96.4% had visited a dentist over the observation period. Two fifths, 42.5%, reported having pain during treatment and one-fifth, 19.1%, had pain that was moderate to severe in intensity. Reports of pain were associated with the types of treatment received, and a number of baseline sociodemographic and psychological factors. In a logistic regression analysis predicting the probability of pain, a variable documenting the number of types of invasive treatment received (restorations, extractions, crowns/bridges, root canal therapy and periodontal treatment/surgery) had the strongest independent effect. Pain was also more likely to be reported by those with previous painful experiences and those who were anxious about dental treatment, expected treatment to be painful and felt that they had little control over the treatment process. Pain was less likely to be reported by those who said they were unwilling to accept or tolerate pain. Younger subjects and those with higher levels of education were more likely to report pain than older subjects and those with a lower educational level. These results indicate that pain is as much a cognitive and emotional construct as a physiological experience. They also have implications for dentists' behaviour when providing dental care.