Aims: (1) To use psychometrically sound measures to characterize the pain levels and pain-related interference associated with recurrent aphthous ulcers (RAU); (2) to determine whether subjects with RAU report clinically significant psychologic symptoms; and (3) to examine the relationships between physical characteristics and self-reported psychologic symptoms, pain, and pain-related interference. Methods: Forty-seven subjects with RAU and an active ulcer completed the Graded Chronic Pain Scale and the Symptom Checklist-90R (SCL-90R). Ulcers were photographed for measurement, and subjects rated pain levels on a 0-to-10 scale before and after swabbing of the ulcer with a saturated solution of sodium chloride and distilled water. Results: Mean characteristic pain intensity was 4.76, with a pain-related interference score of 1.21. None of the average SCL-90R subscale scores were considered elevated. In the model predicting pain intensity after swabbing, pain intensity before swabbing explained 43.6% of the variance (P = .000). Neither the addition of physical characteristics (R2 change = .04; P = .28) nor psychologic characteristics (R2 change = .09; P = .83) contributed significantly to the model. In contrast, only psychologic characteristics contributed to the variance explained in the model predicting pain-related interference (R2 change = .505; P = .007). Conclusions: RAU is a moderately painful condition causing some impairment in functioning. Self-reported pain intensity of a sore does not appear to be influenced by psychologic characteristics. However, pain-related interference appears to be related to psychologic and not physical characteristics. Palabras clave: pain, psychology, recurrent aphthous ulcers