Aim The aim was to examine the prevalence and characteristics of pain and discomfort from root-filled teeth in an adult Swedish population regularly attending dental care. A further aim was to examine if symptoms could be related to (i) periapical radiographic appearance and (ii) clinical findings. Methodology This cross-sectional observational study screened all adult patients scheduled for routine check-up in the public dental service, Örebro County, Sweden in April 2015. All (798) individuals with at least one root-filled tooth were asked to participate. The examination included (i) clinical examination, (ii) radiographic examination (intraoral periapical images), (iii) interviewer-assisted questionnaire covering general health and presence and characteristics of pain. Descriptive statistics were performed and Fisher’s exact test analysed correlations. Results 549 patients with 1256 root-filled teeth participated (292 women, 257 men; mean age 61.1 years, range 20–94). 55 (10.0%) of the patients experienced pain or discomfort from at least one root-filled tooth. On tooth level, 66 (5.3%) of all root-filled teeth were symptomatic. The average pain intensity was 2.2±1.9 on a 0–10 Numeric Rating Scale, and mean pain duration was 32.6 months. The pain was continuous for 21.3%, recurrent for 44.3%, and occasional for 34.4% of the teeth, and the teeth had been painful on average 9.6 of the last 30 days. Apical radiolucency was recorded at 264 (21.6%) of the root-filled teeth. Symptoms were significantly associated with presence of radiolucency (P=0.004), sinus tract (P=0.023), and pocket depth >5mm (P=0.038). Conclusions In the examined population, one in ten adults with a root-filled tooth experienced pain or discomfort associated with this tooth. The pain was generally of low intensity and long lasting. In most cases, the patient experienced recurrent or occasional pain, but one in five with painful teeth had continuous pain.