Some restorative materials are susceptible to erosion but whether it also causes microleakage is still questionable. The aim of this study was to assess the microleakage of few restorative materials after immersion in acidic solution. Standardized ‘U’ shaped cavity of 4mm diameter and 2mm depth were prepared on buccal or lingual surface of 52 human premolar and molar teeth. The teeth were divided into 4 groups which contains 13 samples and 3 controls for each and were restored either with Filtek Z250 (Group 1), Fuji IX (Group 2), Fuji II LC (Group 3), or Silverfill amalgam (Group 4). All surfaces were painted with nail varnish leaving only 2mm of tooth structure surrounding the restoration before the study samples were immersed in acidic solution, lemon juice (pH 2.74) and control samples in deionised distilled water for 24 hours. Surface photos for erosion were taken before immersion in methylene blue for 7 days. After sectioning, the assessment of dye penetration was done using Leica Imaging System DMLM (Germany). Photos showed that Fuji IX demonstrated severe erosion but no obvious changes were seen on other materials. Kruskal-Wallis test indicated that microleakage between all four groups were statistically significant. The most significant difference was between Filtek Z250 and Fuji IX (p<0.05). Fuji IX was the most affected by the erosion process and its degree of microleakage was the most among all the materials tested.