The fumarate reductase (flavocytochrome cs) from Shewanella frigidimarina (formerly S. putrefaciens) NCIMB400 has been crystallized in the space group P2(1), with cell dimensions of a = 45.447 Angstrom, b = 92.107 Angstrom, c = 78.311 Angstrom, and beta = 91.038 degrees and one molecule per asymmetric unit. A native data set has been collected to 1.8 Angstrom. The gene encoding Fcc(3) from the S. frigidimarina type strain ACAM591 has been cloned and sequenced and the protein crystallized in space group P21 with cell dimensions of a = 45.359 Angstrom, b = 88.051 Angstrom, c = 77.473 Angstrom, and beta = 104.499 degrees. Anomalous data have also been collected from the NCIMB400 crystal allowing the heme iron positions to be identified.