Aspocid 75 mg chewing tablets (pH = 3) is the usual drug used in children with heart disease, this acidic medicine is available in Egyptian markets and accessible by the public. This may lead to increase their susceptibility to dental erosion.The aim of this study was to compare the effect of chewing aspocid on the micro hardness of primary teeth and comparing it with that of its soluble form. total number of thirty six exfoliated primary teeth were randomly assigned to two groups after measuring micro hardness at base line: group (A) Exposed to chewing aspocid tablets under vibration to mimic the chewing process, group (B) Exposed to 100 ml aspocid solution. All teeth were prepared for micro hardness test after acidic treatment. Results: Microhardness decreased in both groups. However group (A) showed higher reduction in its micro hardness values than group (B).