A Boundary Element Method (BEM) for the calculation of hydrodynamic characteristics and Flow analysis, including cavitation, is presented. The effectivenessof the method is demonstrated with results for a partially cavitating, three-dimensional hydrofoiland a marine propeller. The method employs source and dipole singularities, which give an integral equation on body and cavity surfaces, to obtain the cavity shape and hydrodynamic characteristics of the cavitating hydrofoils.A nonlinearformula of the dynamic boundary condition was applied for determining the potential on the cavity surface. The effect of the cross-flow was considered when calculating the velocityon the cavity surface. The lift and drag coefficients, pressure distribution and cavity shape of the hydrofoil were calculated and compared with experimental results for a cavitating hydrofoil. The calculated results show good agreement with the experimental values. Flow velocity fields around the cavitating hydrofoils were also investigated by the present method. The method was extended to a marine propeller(with cavitation) and, again. good comparisons Were found. However, further improvement can. be made if the definitionof the cavity separation and cavity trailing edge is improved in order to achieveexact cavity area.