Cyclosporin 'A' is a cyclic peptide and was originally isolated from a soil fungus. The compound is typically used to reduce the body's natural immunity in patients who receive kidney, liver and heart transplants and can also be used to treat severe cases of psoriasis and rheumatoid arthritis diseases. Cyclosporin 'A' is in common usage for kidney and other organ transplants as an anti-rejection medicine. So its importance can not be denied. In the present work, nine local strains of Aspergillus terreus were tested for the production of Cyclosporin 'A' and one best among them was selected for further study. The composition of cultivation medium highly affects the metabolite production by fungi, so carbon and nitrogen sources were optimized for the cultivation medium using the selected strain of Aspergillus terreus. The estimation of extracted Cyclosporin 'A' was carried out through HPLC (High Performance Liquid Chromatography).