Statement of Problem: Microleakage presents the major cause for restorations failure in the oral cavity resulting in postoperative sensitivity, pulp irritation and secondary caries formation.

Aim: The aim of this study was to compare two dentinal adhesive systems of fifth generation and copalite varnish in reducing microleakage of amalgam restorations in primary teeth.
Materials and Methods: In this in-vitro study, 100 class V amalgam restorations were prepared on the buccal or lingual surfaces of primary molar and canine teeth. Samples were randomly divided into four groups (25 samples each). No liner was used for the first group and the second group restorations were lined with copalite varnish. Two dentin adhesives, called Syntac C and Single Bond, were used for the third and fourth groups, respectively. At the next stage, the samples were immersed in 5% fuschin solution for 24 hours, then sectioned buccolingually, and examined under a stereomicroscope for microleakage evaluation.
Results: There was a significant difference between four groups statistically (PO.000I), Comparing four groups, the first and fourth ones, demonstrated the most and the least microleakage, respectively.

Conclusion: The present study showed that new dentinal adhesive systems caused microleakage reduction in amalgam restorations of primary teeth.