This present paper reviews the lichen diversity around the world with special reference to North eastern region of India, particularly in Assam. The various workers have tried to document the lichen diversity in this one of the biodiversity hotspots region of the world. These exploration works have contributed new additions to lichen species and thereby enriching the biodiversity record of a particular geographical region. Lichens are also known to possess secondary metabolites and are reported to show bioactivity, mainly the antimicrobial activity against various microorganisms. This may be very helpful in the field of pharmaceutical sciences as a new potent source of antibiotics. The bioactivity works performed by various scientists using lichen species against certain microorganisms have been briefly discussed in this article.