Femtosecond time-resolved measurements of the optical Kerr effect in molten caesium chloride have been made. Amplified laser pulses of 115 fs duration and 1 mu J energy were used to induce a birefringence. The transmission of a weak probe pulse of the same duration gives a value of 180 fs for the relaxation time of the induced birefringence; this value is consistent with that expected for binary ionic collisions. The magnitude of the Kerr coefficient is estimated to be approximately=3*10^-22 m³ V^-2 (3*10^-13 esu).