(S)-p-Hydroxy-mandelonitrile lyase from Sorghum bicolor has been crystallized in three different forms using the hanging-drop vapor-diffusion technique. Crystal form I is obtained from 1.4 M (NH(4))(2)SO(4) in 100 mM Na-acetate, pH 4.6, and belongs to the orthorhombic space group P2(1)2(1)2(1). The cell dimensions are a = 71.4, b = 95.8, c = 149.1 A. A complete set of diffraction data has been collected to 2.6 A resolution. Form II crystals are grown from 500 mM Li(2)SO(4) in 13% polyethylene glycol 8000. These crystals appear as hexagonal plates and diffract to 2.98 A resolution but apparently are twinned. Cocrystallizing hydroxynitrile lyase with the inhibitor benzoic acid using 1.4 M (NH(4))(2)SO(4) in 100 mM Na citrate, pH 5.4 as precipitant yields crystal form III, which belongs to the monoclinic space group C2 with a = 150.7, b = 103.7, c = 90.6 A, beta = 101.3. X-ray diffraction data were collected to 2.3 A resolution.