The growth of CuInS2 thin films by coevaporation has been monitored by in situ electrical conductivity measurements. Films with different cation ratio In/(In+Cu) were investigated. During the controlled cool-down period we obtain conductivity versus temperature data which are completed ex situ in the low-temperature region. The formation of the semimetallic CuS phase in Cu-rich films is found during the cool-down period at a substrate temperature of about 450 K. For In-rich films the dominance of charged grain boundary states is discussed. © 1997 American Institute of Physics.