Opportunistic infection is common following renal transplantation. Prompt diagnosis and management can be life saving. Four different types of opportunistic respiratory infections diagnosed at our center during the period of January 1998 to December 2000 are discussed. Of the four cases one had Aspergillus, second had Sporothrix, third had Nocardia and fourth case Actinomyces species. Microbiologist has an important role to play by being aware of such opportunistic infections and helping the clinician to make early aetiological diagnosis.