TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn scaled laboratory experiments, we investigated the interaction of a propagating hydraulic fracture with natural discontinuities. We observed the hydraulic fracture geometry as a function of horizontal stress difference, stress regime, flow rate and discontinuity pattern. We observed the smallest amount of interaction for high flowrates. When the horizontal stress difference was increased, the fracture was smoother. However, when we represented the tectonic stress ratio's, with a lower vertical stress compared with the maximum horizontal stress, we observed a higher fracture tortuosity.