In this work we study the instability of the relative equilibria of the Ham
iltonian system corresponding to asymmetric sleeping tops when a viscous di
ssipative perturbation is added. To do this, we consider, for the unperturb
ed problem, the classes of asymmetric sleeping tops for which the relative
equilibria of the linearized Hamiltonian system are spectrally stable at a
range of angular velocities. For these classes we determine the movement of
the eigenvalues of the underlying Hamiltonian system which is initially on
the imaginary axis. (C) 2001 Elsevier Science Ltd. All rights reserved.