The present study was undertaken in order to test the hypothesis that psychological stress is a provoking factor in attacks of recurrent aphthous ulceration (RAU). The population consisted of 22 patients (17 women, 5 men; mean age 39 yr, variation 17-69) with minor RAU. Psychologic stress was evaluated by means of the social readjustment rating scale (SRRS) and a visual analog scale (VAS). In each subject evaluation took place twice: once in the presence of new ulcer(s) and once in the absence of subjective and objective symptoms of RAU. At both stages, the SRRS scores were obtained on the basis of the preceding 2 wk and, VAS scores on the basis of the preceding week. The results showed no statistically significant differences in neither SRRS nor VAS scores between the two stages. Thus, no association between psychologic life stress and recurrences of RAU could be demonstrated, and it is concluded that more standardized circumstances are needed if any such association should be demonstrated.