In this work we present the growth and spectroscopic investigation of Er3+ in CaWO4 single crystals. Er3+ polarized absorption has been measured at room temperature from UV to 1700 nm, and the fluorescence from the most important emitting states from the visible to the infrared has been recorded at 10 and 300 K in the two possible polarizations. The lifetimes of the lower lying excited states have been measured as a function of the temperature to evaluate the contribution of nonradiative decay processes. The absorption spectra enabled us to determine radiative lifetimes of the emitting states by means of the the Judd-Ofelt approach. The stimulated emission cross section has been estimated for the 1.5 mu m transition. A comparison of the theoretical and experimental results permitted to obtain an estimate of the actual Er3+ doping level. A calculation of the effective gain cross section for the 1.5 mu m transition is also presented. These experimental results are discussed in order to evaluate the potentialities of Er3+ in this material as active medium in solid state laser devices. (c) 2007 American Institute of Physics.