Sylvaticin belongs to the elicitin family. These 10 kDa oomycetous proteins induce a hypersensitive response in plants, including necrosis and cell death, but subsequently leading to a non-specific systemic acquired resistance (SAR) against other pathogens. Sylvaticin has been crystallized using PEG 2000 MME as a precipitant agent in the presence of nickel chloride. The crystals belong to space group C2, with unit-cell parameters a = 99.29, b = 25.67, c = 67.45 A, beta = 99.66 degrees. Diffraction data were recorded to 2.1 A resolution at a synchrotron-radiation source.