2004 Conference on Diff. Eqns. and Appl. in Math. Biology, Nanaimo, BC, Canada. Electronic Journal of Differential Equations, Conference 12, 2005, pp. 57-64. Title: On the isospectral beams Author: Kazem Ghanbari (Sahand Univ. of Technology, Tabriz, Iran) Abstract: The free undamped infinitesimal transverse vibrations of a thin straight beam are modelled by a forth-order differential equation. This paper investigates the families of fourth-order systems which have one spectrum in common, and correspond to four different sets of end-conditions. The analysis is based on the transformation of the beam operator into a fourth-order self-adjoint linear differential operator. This operator is factorized as a product $L=H^{*}H$, where $H$ is a second-order differential operator of the form $H=D^2+rD+s$, and $H^{*}$ is its adjoint operator. Published April 20, 2005. Math Subject Classifications: 34B05,34B10. Key Words: Isospectral, Euler-Bernoulli equation for the vibrating beam, beam operator