Glutaredoxin Grx1p from yeast was crystallized both as an independent protein and in a protein fusion with His-tagged yellow fluorescent protein (rxYFP). A glutathionylated C30S mutant of the 12 kDa Grx1p was crystallized in two different forms in PEG 4000 at low pH. These orthorhombic and monoclinic forms diffract to 2.0 Å (synchrotron radiation) and 2.7 Å (rotating-anode generator), respectively. In contrast, rxYFP-Grx1p formed crystals at high pH in MgSO₄ which diffract synchrotron radiation to 2.7 Å.