 The study investigates the biological synthesis of silver nanoparticles from a supernatant of endophytic fungus alternaria sp isolated from refanous sativus leaves, characterizes them using UV vis spectroscopy, FTIR, XRD, DLS, TEM and AFM and finds that they are spherical with an average size of 4 to 30 nanometers and highly toxic against human pathogenic bacteria. This article was authored by Tej Singh, Kumari Juti, Amar Putnayek and others.