The generation of ultrasound by pulsed laser and the detection of these waves by interferometry, shortly called laser ultrasonics, presents many advantages for steel applications because it permits the transduction of ultrasonic waves at a significant distance. Nowadays, this technology is well established in the aeronautical field and is beginning to be used in metallurgy and in the steel industry. This paper describes the physical principles and the technological features of laser ultrasonics. Different examples of present and future applications in the steel industry are presented. They concern different fields, the most important are the monitoring of microstructure in real-time and at high temperature and the on-line measurement of thickness.