Cyanobacteria are unicellular, photoautotrophic, prokaryotic organisms. Due to their ubiquitous nature, they have to endure all environmental conditions as well as changes. During the growth, they have to experience morphological and physiological adaptations. Heavy metals have been released to the environment over long periods of time by natural process and manmade activities. These metals are directly or indirectly involved in all phases of ecosystem as beneficial in extremely narrow ranges, tolerating or toxic to biotic components. Filamentous cyanobacteria are excellent indicators to study the toxic metabolic levels of heavy metals. They differ in their nutritional requirements and also adaptations to changes in availability of nutrients. In the present study two abundantly growing filamentous cyanobacterial isolates Nostoc and Oscillatoria were selected using Allen's and Arnon's as best growth media. These filamentous cyanobacterial species have ability to grow in mass quantity under growing conditions which provides usable biomass at minimum efforts. These isolates were then examined for their ability to tolerate selected heavy metals (As, Cu, Hg and Pb) under experimental conditions by the dilution method. Both the cyanobacterial isolates showed various degree of tolerance for selected heavy metals. The isolate of Nostoc was found to tolerate the presence of all the selected heavy metals as compared to Oscillatoria.