The clinical effects of the Nd:YAG laser operating in both the photodisruptive (Q-switched) and thermal (free-running, cw) modes are discussed, and their clinical applications investigated. Moreover, the physical background of the working modes is explored. When working in the photodisruptive and fundamental (TEM<sub>00</sub>) modes, it is possible to carry out delicate clinical tasks with minimally invasive effects. When the laser is being used in the multimode regime, tasks that are highly resistant to photodisruptive laser radiation can be undertaken. In the thermal mode, photocoagulation can be performed. Nd:YAG laser light (1,064 nm) has high optical tissue penetration and good hemostatic properties, particularly when it is being operated in the frequency-doubled mode (KTP laser).