Two recessive mutations of the cellular slime mold D. discoideum phgA1356 and phgB1351, which express altered phagocytic properties, were characterized using parasexual genetic analysis. The phgA locus was assigned to linkage group VII and the phgB locus to linkage group IV. Complementation analysis of a further 12 independently derived phagocytosis mutants showed that each fell into 1 of these 2 complementation groups.