The purpose of this report was to present the 12-month results of a prospective, randomized study evaluating the clinical and radiographic success rates of Class II adhesive restorations in pulpectomized primary molars. A total of 75 restorations were placed over root canal-treated primary molars, filled with a calcium hydroxide paste. The restorative systems tested were: (1) group 1: amalgam (negative control); (2) group 2: a hybrid resin composite (TPH, Dentsply) with prior acid conditioning and bonding with an etch-and-rinse adhesive (Prime&Bond NT, Dentsply); (3) group 3: a polyacid-modified resin composite (Dyract, Dentsply) bonded with Prime& Bond NT; (4) group 4: Dyract with prior nonrinse conditioner (NRC) treatment and bonding with Prime& Bond NT; and (5) group 5: a polyacid-modified resin composite (F2000) in conjunction with a self-etch adhesive (Prompt-L-Pop, 3M/ESPE). The restorations were evaluated clinically using the modified USPHS/Ryge criteria at 1, 2, 3, 4, 5, 6, 9, and 12 months. Radiographic evaluations were made in accordance with predetermined criteria. During the evaluation period, 12 teeth (group1=4, group2=1, group3=4, group4=3, and group5=2) were extracted due to radiographic evidence of failure. There was no difference between groups regarding the clinical evaluation criteria (P>.05) except marginal discoloration at 9 and 12 months (P<.05). The overall success rate at 12 months was 81% (group 1=73%, group 2=93%, group 3=73%, group 4=80%, and group 5=87%). Teeth restored with the resin composite+total-etch/bonding (group 2), followed by those with F2000+self-etch adhesive (group 5) exhibited the highest clinical and radiographic success rates. Radiographic failures observed beneath failed restorations were strongly suggestive of coronal micro-leakage.