Based on data generated by the European Standard EN 1007-5 - used for the characterization of the tensile behaviour at room temperature of multifilament tows made of continuous ceramic filaments - this paper describes an adjustment of mixture of two Weibull distributions to the fibres' fracture data. The statistical modelling is illustrated with data on a large range of stress and strain values. Parameter estimates are obtained using maximum likelihood method implemented at R software (version 1.6.2, 2003-01-10) from Free Software Foundation's GNU General Public License.