Hydroxy benzisoxazole 1 was converted into chlorobenzisoxazole 2 and then to hydrazinobenzisoxazole 3 . New tricyclic compounds, triazolobenzisoxazole 4 was obtained from hydrazinobenzisoxazole when treated with formic aci d. Similarly 3-hydroxytriazolo benzisoxazole 5 and 3-mercaptotriazolobenzisoxazole were prepared by the action of urea and CS 2 in alkali respectively. The compounds have been c haracterized by elemental analysis and spectral data. Newly synthesized compounds have be en screened for their antimicrobial activities against several microbes.