AET has been used to study the effect of in inclusions on the acoustic emission (AE) generated during tensile deformation and fracture of AISI type 316 stainless steel. The amplitude distribution analysis approach has clearly revealed the generation of more number of events with higher peak amplitudes in commercial grade steel as compared to nuclear grade steel. An innovative technique has been developed to amplify the weak AE signals generated during deformation of austenitic stainless steels. This is based on the understanding that external injection of ultrasonic waves simultaneously during tensile deformation is expected to interact with the subcritical AE sources and give rise to enhanced AE signals which otherwise would not have got released at those stress levels. AET has also been used for detecting the micro plastic yielding occurring during macroscopic plastic deformation in 316 SS. AE generated during tensile testing due to operation of Frank-Reed and grain boundary sources in solution annealed Nimonic alloy PE-16 has been compared with the AE generated due to particle shearing and Orwan looping processes taking place in presence of and decohesion and fracture of MC type carbides occurring during tensile deformation. AET has also been used for detection and assessment of FCG in 316 SS. The two substages in the state II paris regime of FCG could be distinguished by a change in the rate of acoustic activity with increase in crack growth rate. The potential of the AET for on-line monitoring of ' - martensite formation has been established. AE from -martensite formation occurring during mechanical and thermo-mechanical treatment has conclusively established the effect of prior cold work on subsequent ' - martensite formation. AET with advanced spectral analysis techniques have been employed for detection of minute leaks in noisy environments, with high sensitivity.