Lamb wave inspection is one of the most widely used damage detection techniques based on ultrasonic waves. Many signal processing techniques have been developed for extraction of signal features related to damage. The majority of these investigations focus on amplitude analysis. The paper analyses Lamb wave instantaneous phase and frequency. The Hilbert transform is used to obtain signal instantaneous characteristics. Application examples are related to smart structural repair. Cracked metallic plates are repaired using bonded aluminium patches instrumented with low-profile, surface bonded piezoceramic transducers. The study demonstrates that phase and frequency information from Lamb waves is very useful for monitoring structural repair.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.