The Boundary Element Method is applied to synthesize a set of Boundary Integral Equations representing the uncoupled axial and flexural dynamic behavior of rectilinear Bernoulli-Euler beam elements in the frequency domain. In the sequence, these structural elements are coupled by the sub-region technique to model two-dimensional frame structures, in which the axial and flexural behaviors are coupled. This methodology is used to accurately recover modal data, eigenfrequencies and eigenmodes, of two frame structures. The usual Boundary Element procedure is recast to deliver simultaneously the values of variables at the element boundaries and at an arbitrary number of internal nodes. The inclusion of internal nodes allow to recover the structure eigenmodes and makes feasible the coupling of the assembled systems with a surrounding environment, for instance, an acoustic field. The results obtained are compared with a standard Finite Element eigenvalue analysis. It is shown that for increasing response frequencies, the Boundary Element scheme delivers modal data within a degree of accuracy, which is only obtained by the conventional Finite Element Method with considerable finer meshes. (C) 2000 Elsevier Science Ltd. All rights reserved.245399406