Salmonella FlgA, a periplasmic protein essential for flagellar P‐ring assembly, has been crystallized in two forms. The native protein crystallized in space group C222, with unit‐cell parameters a = 107.5, b = 131.8, c = 49.4 Å, and diffracted to about 2.0 Å resolution (crystal form I). In this crystal, the asymmetric unit is likely to contain one molecule, with a solvent content of 66.8%. Selenomethionine‐labelled FlgA protein crystallized in space group C2221, with unit‐cell parameters a = 53.2, b = 162.5, c = 103.5 Å, and diffracted to 2.7 Å resolution (crystal form II). In crystal form II, the asymmetric unit contained two molecules with a solvent content of 48.0%. The multiple‐wavelength and single‐wavelength anomalous dispersion methods allowed the visualization of the electron‐density distributions of the form I and II crystals, respectively. The two maps suggested that FlgA is in two different conformations in the two crystals.