Stevia rebaudiana is an herb with a very high medicinal value. It has more than 100 phytochemicals. It is used as sugar substitute. The extracts from leaves are used for the microbial assay and study the antimicrobial activity. The microbes used for the testing the activities are E.coli, Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, Aspergillus niger, Candida parapsilosis, Trichophyton rubrum. With different concentrations of the extracts starting from 2.5µg/ml, 5.0µg/ml, 7.5µg/ml, 1.0µg/ml and the highest activity is shown by Staphylococcus aureus and Candida parapsilosis.