We present a method for the numerical computation of tear propagation in soft hydrated biological tissues. The tissue is modelled using the Theory of Porous Media (TPM) which allows for the description of multi–component continua with internal interaction. For the numerical treatment of the tearing mechanism, the Extended Finite Element Method (XFEM) is applied. By use of an energy configuration scheme, stress intensity factors (SIFs) are computed to evaluate the tear extension regarding a maximum hoop stress criteria. The arising opening in the tissue is considered as to be connected to an external fluid reservoir and is thereby loaded with differing pressures. Numerical examples show the influence of this pressure loading on the interstitial pressure development during a Mode I tearing experiment. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)