Optical absorption and emission properties of Er3+ions inZnCl2-based glasses are investigated. The electric dipole line strengths for various transitions were estimated from the measured optical absorption spectra. The spontaneous emission probabilities for various transitions were predicted using the Judd–Ofelt theory. Among&OHgr;t(t=2, 4, 6)phenomenological intensity parameters, the&OHgr;2value is larger than that measured for ZrF4-based glass. On the contrary, the&OHgr;4and&OHgr;6values are comparatively small. Multiphonon relaxation rates follow a so-called “energy-gap law” which is given byWMPR=C exp(−&agr;&Dgr;E). TheCvalue is quite smaller than that of the ZrF4-based glass by about two orders of magnitude. This result is attributed to the very low-phonon-energy of the chloride glass matrix. On the other hand, the&agr;value is almost the same as those of other glass hosts. Because of the low-phonon-energy and the host-independent&agr;value, the electron–phonon coupling constant&egr;of theZnCl2-based glass is extremely large compared with those of oxide and fluoride glasses. It was also found that several emissions due to transitions between the excited 4f-levels are detectable, which are hardly observed in other glass hosts. Radiative quantum efficiency is definitively high even for emitting levels of which the energy-gap to the next-lower level is small. ©1997 American Institute of Physics.