Time-resolved photoluminescence of CuInS2 crystals has been investigated under high excitation power density. A new observed emission at 1,533 eV at low temperature that is between free exciton and a bound exciton. This emission exhibits very fast decay and can be attributed to radiative recombination of biexciton as determined from the results of excitation power density dependence. The binding energy of biexciton is estimated to be 1.6 meV. (c) 2005 Elsevier B.V. All rights reserved.