  The longitudinal ultrasonic attenuation at low temperatures for a $d$-wave
superconducting order parameter is examined. The ratio of the superconducting
to normal state attenuation, $\alpha_{s}/\alpha_{n}$, depends strongly on the
direction of propagation of ultrasound with maxima corresponding to nodes of
the order parameter on the Fermi surface. We propose that measurements of
ultrasonic attenuation in a single crystal of the high-$T_{c}$ superconductors
can give the information regarding the position of nodes.
