A new myotoxic Lys49-phospholipase A2 isolated from Bothrops moojeni snake venom has been crystallized. The crystals diffracted to 2.18 A resolution using a synchrotron-radiation source and belong to space group C2. The unit-cell parameters are a = 56.8, b = 125.0, c = 64.7 A, beta = 105.5 degrees. Preliminary analysis indicates the presence of four molecules in the asymmetric unit. This may suggest a new quaternary structure for this Lys49-phospholipase A2 in contrast to the dimeric and monomeric structures solved so far for this class of proteins.