The antimicrobial activity of 90% ethanol, methanol, ethyl acetate and aqueous extracts of leaves of Sida acuta was investigated to verify its claimed ethno medicinal use as an antimicrobial agent and comparative study of different extracts was carried out. The antimicrobial activity of the different extracts was tested against standard strains and clinical samples of some bacteria and fungi using agar well diffusion method. Commercial antibiotics were used as positive standard references to determine the sensitivity of the strains. All the extracts showed significant inhibitory activity against gram positive bacteria (Bacillus subtilis, Staphylococcus aureus), gram negative bacteria (Escherichia coli, and Proteus vulgaris), fungi (Candida albicans and Aspergillus niger) and clinical isolates of Staphylococcus faecalis, Staphylococcus aureus and some gram positive bacteria. The range of zone of inhibition was found to be 10-30 mm and minimum inhibitory activity was as low as 2 µg/ml. The zone of inhibition was highest with ethanol extract followed methanol, ethyl acetate and aqueous extracts for all the microorganisms used. Aqueous extract was effective only on P. vulgaris.