The molecular structure of a triclinic crystal form of concanavalin A has been refined at 2.4 Angstrom resolution. The crystals have unit cell dimensions a 78.8 Angstrom, b = 79.3 Angstrom, c = 133.3 Angstrom, alpha = 97.1 degrees, beta = 90.2 degrees, and gamma = 97.5 degrees and contain two tetramers per asymmetric unit each with approximate 222 symmetry. The final crystallographic R-factor is 0.205 and the free-R-factor is 0.265 in the resolution range 6.0 to 2.4 Angstrom The conformation of the tetramer is more similar to that found in concanavalin A saccharide complexes than in the previously reported I222 crystal form of uncomplexed concanavalin A. A comparison of the molecular packing between the two crystal forms shows a more open arrangement with large solvent channels through the crystal. (C) 1996 Academic Press, Inc.