This study describes the formation of Fe-doped chrysotile fibers with partial and total substitution of Mg by Fe. Syntheses were carried out with various starting mixtures (oxides, pure synthetic forsterite) in an externally heated pressure vessel in controlled hydrothermal conditions: temperature, 270 – 400 °C; pressure, 0.5 – 2 kbar; duration of treatment 160 – 480 hours. Pure synthetic forsterite was prepared by the flux growth technique. The starting material and run products were characterized by X-ray powder diffraction (XRPD), scanning and transmission electron microscopies combined with energy-dispersive spectrometry (SEM-EDS and TEM-EDS), differential scanning calorimetry (DSC) and thermogravimetry (TG). Variations observed in abundance and size of Fe-doped chrysotile fibers were attributed to different experimental conditions for their synthesis. However, morphological shape turned out to depend on the starting mixtures used. Since natural samples are often difficult to obtain in a sufficiently pure state, these synthetic and well-characterized Fe-doped chrysotile fibers can be used for better understanding of the mechanisms involved in asbestos toxicity, as well as of the role of Fe in diseases induced by asbestos phases. These synthetic Fe-doped chrysotile fibers, together with non-toxicity testing, may also have potential for exploitation in industrial fields. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)