Selenium-incorporated osmotically inducible protein C from the thermophilic bacterium Thermus thermophilus was overexpressed, purified and crystallized. The crystals belong to space group P1, with unit-cell parameters a = 37.58, b = 40.95, c = 48.14 A, alpha = 76.93, beta = 74.04, gamma = 64.05 degrees. Five data sets were collected from a single crystal to 1.6 A using synchrotron radiation for MAD phasing. Self-rotation functions and the Matthews coefficient are consistent with two molecules in the asymmetric unit.