THE PRESENT INVENTION IS DIRECTED TO THE USE CHITOSAN, A CHITOSAN DERIVATIVE OR A PHYSIOLOGICALLY ACCEPTABLE SALT THEREOF, TO INCREASE NAIL GROWTH RATE. THE INVENTION IS FURTHER DIRECTED TO THE USE CHITOSANS TO ACCELERATE NAIL GROWTH RATE DURING TREATMENT OF NAIL ILLNESSES, NAIL DYSTROPHY OR OTHER NAIL CONDITIONS, IN ORDER TO SHORTEN CONSIDERABLY THE SPECIFIC TREATMENTS OF SAID NAIL ILLNESSES, NAIL DYSTROPHY OR OTHER NAIL CONDITIONS.