In the diagnosis of respiratory diseases, sputum induction has played an important role in the diagnosis of various respiratory diseases over the years. It is also being used increasingly to study pathophysiology of various respiratory diseases. For bronchial asthma diagnosis, Curschmann’s Spirals and Charcot Leyden crystals are popularly used to diagnose the condition. Sputum cytology for presence of malignant cells and various biochemical markers in sputum are also used for the diagnosis as well as a prognostic marker during follow-up cases of suspected lung cancer. In various respiratory infections, isolation of various pathogens e.g., bacteria, fungi, viruses are helpful in diagnoses of respiratory infections in the sputum analysis.