This paper discusses laboratory studies to determine the nature of channel growth and stability in proppant packs with and without fibers. Tests were performed with proppant packs in three different types of experiments using natural sand and ceramic proppants, gas and water flow, and either perforations or an open proppant pack face. Proppant packs without fibers fail at low fluid velocities by the formation of voids at perforations or across the entire front ofthe pack. In proppant packs without fibers, channels form only in cases when packing is imperfect. Proppant packs with fibers form channels 2-10 cm wide, depending on fluid velocity. The channel length increases in stepwise progression with increasing flow rate (velocity). The proppant pack on either side of the channel supports the closure stress. Channels are stable over time at constant flow rate and remain stable during closure stress cycling. Channels grew with fibers in all conditions tested. Random fibers mixed with the proppant extend the fluid velocity range for channel growth to much higher values.