The lattice-gas automata and lattice Boltzmann (BGK) methods were used to estimate the mixing of fluid streams at a continuous fracture junction, for Peclet number (Pe) from 0 to 1547. Agreement with experimental results is good, particularly at Pe≤25. At low Pe, a large fracture length/width is needed to obtain accurate mixing ratios (Mr). For a 90¿ intersection of two fractures with equal widths and flow rates, Mr approaches 0.5 (complete mixing) at Pe≈1. At the highest Pe studied, Mr=0.022, in contrast with the streamline routing prediction Mr=0.¿ 1997 American Geophysical Union