Two-dimensional reaction-diffusion equations with simple reaction kinetics are used to study
the dynamics of spiral waves in excitable media. Detailed numerical results are presented
for the transition from simple (periodic) rotation to compound (quasiperiodic) rotation of
spiral waves. It is shown that this transition occurs via a supercritical Hopf bifurcation and
that there is no frequency locking within the quasiperiodic regime.