We have demonstrated the use of laser scanning confocal microscope for mapping the refractive index as well as Cr3+ and Cr4+ fluorescence in Cr:YAG crystal fibers with 1 mum spatial resolution. The corresponding sensitivities for Cr3+ and Cr4+ fluorescence intensities are 1.6 x 10(17)/cm(3) and 7.5 x 10(15)/cm(3), respectively. The share of Cr4+ ions in the total Cr concentration is found to be proportional to the ratio of Ca to Cr concentrations. However, only less than 1% of the Ca2+ ions become active in charge compensation. The concentration of Cr4+ ions is higher near the center of the crystal fiber when the core diameter is less than 300 mum. In addition, stress-induced striations created near the fiber center disappear when the fiber diameter is smaller tharl 500 mum. (C) 2004 Elsevier B.V. All rights reserved.