Tracer dispersion in double porosity packings of porous grains obtained by grinding sintered glass samples of various porosities and permeabilities is studied experimentally. The dispersivitylDincreases faster with velocity than for single porosity packings: this variation is predicted by modeling the medium as a one‐dimensional (1‐D) sequence of identical cells with one slow and one fast path in parallel. The grain size and the permeability contrast between the inside and the outside of the grains can also be determined. At low grain porosities, the transit time &tgr;iinsideindividualgrains becomes of the order of the meantransittimeacross thewholesample and non‐Gaussian dispersion curves are observed.