The boundary integral element method based on Green's formula is applied to the analysis of transient flow problem in corrugated bottom tanks. The problem is formulated as a two-dimensional linear, initial boundary value problem in terms of a velocity potential. The Laplace equation and the boundary conditions, except the dynamic boundary condition on the free surface, are transformed into an integral equation by the application of Green's formula. Finite Difference discretization is applied timewise. Initially a triangular wave on the free surface is assumed to be formed. The height of the triangular corrugated bottom is varied between 1/10 and 1/5 of the tank depth. The form of the free surface and the equipotential lines for the flow in the tank are presented at different time steps. An accuracy analysis is performed and distortion in time is considered. Proper coefficients for solutions are derived and presented. The results show that utilization of triangular corrugated bottoms may help to regulate the flow in tanks. (C) 1998 Elsevier Science Ltd. All rights reserved.