Class S proteins of staphylococcal bicomponent pore-forming leucotoxins play an important role in membrane targetting and cell specificity. Wild-type and recombinant S components of the Panton-Valentine leucocidin (LukS-PV) were expressed in Staphylococcus aureus and Escherichia coli, respectively, and purified. Both proteins were crystallized in two crystal forms with Jeffamine M-600 as the precipitant at 285 K using the hanging-drop vapour-diffusion method and seeding techniques. Crystals belong to space group P2 (or P2(1)) and P4(1) (or P4(3)), with unit-cell parameters a = 72.3, b = 95.1, c = 108.1 A, beta = 106.4 degrees and a = b = 94.8, c = 306.2 A, respectively. A full set of X-ray diffraction data was collected to 2.1 A from a single tetragonal crystal of the wild-type protein at 100 K.