Objectives: Recently, flowable composites were offered for restoring to every detail on the cavity.  Tani et al (1983) were reported the glassbeads abrasion test was appropriate for occlusal wear of Posterior composites. The purpose of this study was undertaken to determine wear of six flowable composites; . Materials and Methods: Products: Filtek Flow (FIF, 3M ), Metafil Flo (MEF, Sun Medical ), UniFil Flow (UNF, G.C.), Tetric Flow (TTF, Vivadent), Estelite LV High Flow(EHF,Tokuyama Dental)and Estelite LV Low Flow(ELF,Tokuyama Dental). Palfique Estelite (PAL, Tokuyama Dental), Metafil C (MET, SunMedical), Clearfil AP-X (APX, Kuraray) as controls. Five specimens (10x10x1.5mm) of each material were prepared by photo-curing. All specimens were polished with a 1200 grit SiC papers to wear away 200um from the surface to be tested. After these specimens were kept in a desiccator until they attain a constant weight, specific gravity of each material was measured by an electronic gravity meter. The specimen, fixed in the horizontal drive airm, was reciprocated with a 200g - load in the toothpaste slurry (Lark Sunstar 150 g in 500 ml of water) at a velosityof 120 strokes per minute for 10000 times, onwhich connected five brush parts in series. After ultrasonic cleaning of specimens, they were kept in desiccator. The degree of wear was measured bywhich divided weight loss by specific gravity. Deta were analyzed by ANOVA (p<0.01). Results: 2.100 (cm3 x 10-3) with MEF, 3.647 with UNF, 4.115 with TTF, 4.531 with EHF, 5.335 with ELF, 0.411 with PAL, 2.513 with MET, 2.471 with APX. Conclusions: FILshowed the least wear (p<0.01) among them whereas ELF showed larger wear among them except EHF. As compared with normal composites tested by same methods, toothbrush wear of flowable composites were more higher than normal composites.