Objectives: The purpose of this prospective randomized clinical study was to compare the clinical performance of the new self-etching adhesive system AdheSE One in combination with the composite Tetric Evo Ceram and the influence of the additional application of the flowable resin composite Tetric Flow after six months. Methods: In 50 patients 25 class I and 75 class II cavities were placed with at least two restorations per patient. The adhesive system AdheSE One was used for all the restorations. In one of the two fillings in each patient, an additional layer of the flowable resin composite Tetric Flow was applied in the entire cavity and separately light-cured. The fillings were placed under rubber dam. All materials were used as recommended by the manufacturer. Two clinicians evaluated the restorations at baseline, two week following placement, and at the six month recall visit according to the modified clinical criteria of Ryge. For this sensitivity, hypersensitivity, marginal discoloration, marginal adaption, recurrent caries, surface, color match, proximal contact and filling integrity were considered. All data were analyzed by Man-Whitney-U-test. Results: After six months all fillings could be re-examined. All teeth remained vital and did not show any signs of postoperative sensitivity. Marginal adaption code Bravo could be evaluated in four fillings (three with flowable liner, one without). In one tooth a filling integrity was scored as Bravo (without fowable liner). None of the one hundred teeth showed signs of secondary caries. Statistical analysis showed no significant difference between techniques for any of the evaluation criteria (p>0.05, Man-Whitney-U-test). Conclusions: At this inital phase the use of a flowable composite showed no significant impact on the clinical performance of class-I and -II restorations. The self-etch adhesive AdheSE One might be a promising alternative to other systems. This study was supported by Ivoclar Vivadent, Germany. Keywords: composite, flowables, self-conditioning bonding agent, clinical trial