  A Bohr-Sommerfeld equation is derived for the highly-damped quasinormal mode
frequencies omega(n>>1) of rotating black holes. It may be written as
2\int_C(p_r+ip_0)dr=(n+1/2)h, where p_r is the canonical momentum conjugate to
the radial coordinate r along null geodesics of energy hbar*omega and angular
momentum hbar*m, p_0=O(omega^0), and the contour C connects two complex turning
points of p_r. The solutions are omega(n) = - m*omega_0 - i(phi + n*delta),
where {omega_0,delta}>0 are functions of the black-hole parameters alone. Some
physical implications are discussed.
