Fuculose phosphate aldolase catalyzes the reversible cleavage of L-fuculose-1-phosphate to dihydroxyacetone phosphate and L-lactaldehyde. The protein from Thermus thermophilus HB8 is a biological tetramer with a subunit molecular weight of 21 591 Da. Purified FucA has been crystallized using sitting-drop vapour-diffusion and microbatch techniques at 293 K. The crystals belong to space group P4, with unit-cell parameters a = b = 100.94, c = 45.87 A. The presence of a dimer of the enzyme in the asymmetric unit was estimated to give a Matthews coefficient (VM) of 2.7 A3 Da(-1) and a solvent content of 54.2%(v/v). Three-wavelength diffraction MAD data were collected to 2.3 A from zinc-containing crystals. Native diffraction data to 1.9 A resolution have been collected using synchrotron radiation at SPring-8.