Recent studies on tsunamis are reviewed. Theoretical studies on tsunami generation and propagation have been done both on coupled and decoupled systems of ocean and solid earth. Both approaches are proved to be equivalent. Hydrodynamic formulation, on the basis of decoupling model, is discussed in detail. Several models have been proposed for the mechanism of tsunami earthquakes that produce abnormally large tsunamis compared to seismic waves. After the 1983 Japan Sea tsunami, some progress has been made on tsunami research. Among them are re-examination of tide-gauge system, studies on free oscillation of the Japan Sea and newly developed inversion technique of tsunami waveforms to estimate complex fault motion. Large-scale realistic computation of tsunamis can be made very rapidly and has potential usage for tsunami warning system. These seismology-related problems are described.