AbstractDespite abundant evidence of actin's involvement at the particle internalization stage of phagocytosis, little is known about whether phagosomes undergo the same type of actin‐based motility as observed with endocytic vesicles or such intracellular pathogens as Listeria and Shigella. By employing video microscopy to follow the fate of latex bead‐containing phagosomes within the cytoplasm of bone marrow macrophages, we have made the novel observation of actin‐based phagosome motility. Immunofluorescence microscopy confirmed that phagosomes containing IgG‐opsonized, bovine serum albumin (or BSA) ‐coated or uncoated latex beads all formed actin‐rich rocket tails that persisted only during a brief, 1–2 min period of actin‐based motility. Average speeds of actin‐based phagosome motility were 0.13 ± 0.06 μm/s for IgG‐coated beads, 0.14 ± 0.04 μm/s for BSA‐coated beads, and 0.11± 0.03 μm/s for uncoated beads. Moreover, the speeds and motile‐phase duration of each type of phagosome were comparable to the behavior of pinosomes [Merrifield et al., 1999: Nat. Cell Biol. 1:72–74.]. Determination of optimal conditions for observing and analyzing actin‐based phagosome motility should facilitate future investigations of phagocytosis and phagosome maturation. Cell Motil. Cytoskeleton 53:81–88, 2002. © 2002 Wiley‐Liss, Inc.