The sediments of La Jolla Fan comprise alternating beds of mud and sand. The muds and the upper parts of sand beds are highly disturbed by burrowing animals. The amount of reworking in sand beds can be calculated from the degree of disturbance of the bed. The amount of reworking at the junction of sand and mud beds is estimated by comparing observed distributions of sand sized material in the sediment with distributions obtained by computer simulation of bioturbational processes. There appears to have been no marked change in the intensity of reworking during the last 4000 years. Among individual burrow types recognized are those of the pelecypod Nucula, of a deep water echinoid, and ones formed by animals escaping through rapidly deposited sand beds.