We have investigated the conditions required for polar localization of the CheZ phosphatase by using a CheZ-green fluorescent protein fusion protein that, when expressed from a single gene in the chromosome, restored chemotaxis to a ΔcheZ strain. Localization was observed in wild-type, ΔcheZ, ΔcheYZ, and ΔcheRB cells but not in cells with cheA, cheW, or all chemoreceptor genes except aer deleted. Cells making only CheA-short (CheAS) or CheA lacking the P2 domain also retained normal localization, whereas cells producing only CheA-long or CheA missing the P1 and P2 domains did not. We conclude that CheZ localization requires the truncated C-terminal portion of the P1 domain present in CheAS. Missense mutations targeting residues 83 through 120 of CheZ also abolished localization. Two of these mutations do not disrupt chemotaxis, indicating that they specifically prevent interaction with CheAS while leaving other activities of CheZ intact.