Purpose: To test the marginal adaptation of Class IV restorations made of different composite materials designed for anterior use. Materials and Methods: Forty-two extracted caries-free human maxillary central incisors were randomly divided into 7 experimental groups - one per composite tested - for which Class IV cavities were prepared. The microfilled composite materials tested (SolidBond/Durafill [D/SB], Syntac classic/Heliomolar [H/SC], Scotchbond1/ Experiment127 [EXI/SB1], Optibond FL/Point 4 [P4/OBFL], Prime&Bond NT/Esthet-X [EX/PBNT], ART Bond/ Miris [MIR/ART], SE Bond/Clearfil ST [CLE/SE-B]) were inserted in two increments after polymerization of their respective adhesive systems. While under simulated dentinal fluid pressure, specimens were submitted to cyclic incisal stress (1,200,000 cycles, maximum load 49 N) and thermal loading (3000 cycles). Both after polishing and after thermomechanical loading, impressions were made of the surface of each restoration, and epoxy replicas were prepared for the marginal adaptation evaluation using SEM. Results: Perfect margins before loading in enamel ranged from 49.9% (EXI/SB1) to 98.2% (MIR/ART) and after loading from 25.3% (EXI/SB1) to 91.9% (MIR/ART). For margins located in dentin, perfect margins ranged from 16.8% (EXI/SB1) to 100% (CLE/SE-B) before loading and from 4.6% (EXI/SB1) to 67.1% (CLE/SE-B) after loading. Conclusion: The poor results obtained in this in-vitro test with the microfilled composites suggest avoiding their use in large Class IV restorations with margins in dentin. Keywords: Class IV, marginal adaptation, adhesive restorations, SEM