Fission-track (FT) dating is a radiogenic method of age estimation based on the accumulation of damage trails left by nuclei that are expelled during spontaneous nuclear fission of the uranium isotope 238U. Significant amounts of uranium occur in rock-forming minerals such as apatite and zircon. Data obtained by FT dating such as grain ages of internal and external surfaces, different closure temperatures of both surfaces, and distribution patterns of FT lengths give us valuable information as a geological clock and thermometer. Two examples from the Niigata district demonstrate the application of FT dating.