The morphology of surface-opening burrows made by earthworms in a South Australian duplex Red-brown Earth was investigated. Coordinate points along burrows were measured during careful excavation. Burrow length, orientation and the frequency of branching were measured. Mean burrow length was 398 mm (s.d.=189) with typically 2 to 3 branching points. Polar coordinate representation of the burrows showed them to be nearer to vertical at greater depths. Maximum depth of excavated burrows was approximately 250 mm, placing them almost entirely in the soil A horizon.