Dipeptidyl peptidase 11 from Porphyromonas gingivalis (PgDPP11) preferentially cleaves substrate peptides with Asp and Glu at the P1 position [NH2-P2-P1(Asp/Glu)-P1'-P2' ... ]. For crystallographic studies, PgDPP11 was overproduced in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data to 1.82 angstrom resolution were collected from an orthorhombic crystal form belonging to space group C222(1), with unit-cell parameters a = 99.33, b = 103.60, c = 177.33 angstrom. Structural analysis by the multi-wavelength anomalous diffraction method is in progress.