Streptococcus pneumoniae SP0987, which was identified as a hypothetical protein, has a very low sequence identity to other well characterized lysozyme structures. Since determination of three-dimensional structure is a powerful means of functional characterization, X-ray crystallography has been used to accomplish this task. Here, the expression, purification, crystallization and preliminary crystallographic analysis of SP0987 from Streptococcus pneumoniae TIGR4 are reported. The crystal belonged to space group P2(1)2(1)2(1) (with unit-cell parameters a = 36.46, b = 40.89, c = 147.44 A) and diffracted to a resolution of 1.85 A. The crystals are most likely to contain one molecule in the asymmetric unit, with a V(M) value of 2.02 A(3) Da(-1).