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Dictyostelium serves as an ideal model system for studying the molecular and structural properties of the actomyosin and microtubule systems. This organism also has been the vehicle on which the gene-targeting technique was pioneered. Dictyostelium also represents a small number of organisms whose chemotactic ligand-receptor mechanism has been well characterized. This article reviews recent advances in studies of the actin-based cytoskeletal system in Dictyostelium, focusing on the mechanistic aspects of the amoeboid motion. Special emphasis is placed on the recently identified cell-substrate-anchoring structures ‘eupodia’, and the measurement of single-cell migration forces. The recent advances in signal transduction cascade is also discussed with relevance to the mechanistics in amoeboid locomotion