CsI:Tl monocrystal was studied in the range 360-630 nm to determine the decay-times of its several emission bands. The system was excited in the A-band at 308 nm by means of a Xe-Cl excimer laser. The temperature varies from 30 to 300 K. Many emission bands are observed some of which with slow and fast components. The decay-times range from 1 ns or less to some microsecond. The study of the fast components and the competition in the emission between thee and the slowest ones assumes particular interest in the possible application of this system as active medium for tunable solid state laser around 400 nm. 1 .