Latent damage tracks of energetic 4°Ar ions (18.56 MeV/u) have been recorded in Lexan polycarbonate detector. Bulk and track-etch parameters are evaluated under successive chemical etching. Our results show a linear correlation between the measured track-etch rate along the track and the corresponding total energy-loss rate and predict a threshold value of 5.0 MeV rag-tcm 2 for track registration. Maximum etchable track lengths of 4°Ar ions as a function of energies have also been measured and compared with three different sets of theoretical ranges.