A particle-tracking method has been developed to calculate tracer transport in fractures with diffusion into finite rock matrix blocks. The method is an extension of the work of Yamashita and Kimura <1990>, which is only applicable to diffusion into an infinite matrix. The new method has been verified against a number of analytic or semianalytic solutions for transport in a homogeneous fracture medium with matrix diffusion. The method is applied to the calculation of tracer breakthrough curves for a hypothetical tracer injection-withdrawal experiment in a heterogeneous fracture zone, with variable hydraulic properties and finite matrix blocks. ¿ 2001 American Geophysical Union