Purpose: The aim of this study was to evaluate the effect of daily intake of LongoVital (LV) (herbal vitamin tablets) in the prevention of RAS. Materials and Methods: A group of 78 consecutively referred patients was enrolled to a three-months pretreatment period. Fifty subjects were then randomly allocated to an LV-group (n = 25) or a placebo group (N = 25). A double blind, stratified-randomised clinical case-control study was performed during six months. Number and size of the ulcers were registered by the patients using a standardized chart. The degree of discomfort was recorded on a 100 mm horizontal visual analogue scale (VAS-scale). Results: The three-months pretreatment period revealed that the most dominant symptoms were pain (78%) followed by burning sensation (18%). No significant differences between the two groups were found during this period when a comparison was made at the end of the study. After the intervention period the number of aphthous ulcers/month decreased significantly in the LV-group (p = 0,02). The number of days in pain/month were also reduced (p 0,001). If a 50% reduction of number of aphthous ulcers and days in pain were considered as clinically relevant, no statistical significant differences were found between the groups. Conclusion: Thus, no strong evidence was found that justified a recommendation of LV as a general drug for treatment of RAS. Schlagwörter: recurrent aphthous stomatits, LongoVital, immunostimulation