Five mouse macrophage cell lines were tested for chemotaxis and phagocytosis. All 5 cell lines ingested sheep red cells coated with rabbit IgG anti-Forssman antibody and exhibited chemotaxis to endotoxin-activated mouse serum (EAMS) and lymphocyte-derived chemotactic factor. Two cell lines were tested for chemotaxis to f-Met-Leu-Phe and neither responded. Four of the cell lines (RAW264, RAW309CR, PU5-1R, and WR19M.1) exhibited chemotaxis to C5a. These cell lines displayed a 1- to 2-hr lag before migrating toward EAMS, and chemotaxis was dependent upon cell density. When fewer than 10(3) cells were present per mm2 of filter surface, less than 10% of the cells migrated; however, at a density of 5 X 10(3) cells/mm2 50 to 70% of the cells migrated. WEHI-3 differed from the other cell lines in that there was no chemotaxis to C5a, migration to EAMS did not have a detectable lag, and there was no cell density dependence for chemotaxis. Comparison of these chemotactic properties with those reported in the literature for mouse macrophages and monocytes suggests that RAW264, RAW309CR, PU5-1R, and WR19M.1 have properties that are similar to those of mouse resident macrophages, whereas WEHI-3 may have some of the properties of mouse monocytes.