Crystals of aluminum, oriented for single slip, were deformed up to 1% glide strain. Specimens for diffraction electron microscopy were prepared, and direct observations on dislocations were made. The presence of three‐dimensional tangles as well as small prismatic dislocation loops was established. Considerations have been made as to how the tangles were formed. It was further concluded that dislocations move in glide zones, mainly between tangles which can act as sources for dislocations and as obstacles against their motion.