Human sirtuin 1 is a member of the histone deacetylase family and is involved in cellular aging, tumourigenesis and cellular metabolism. Recombinant sirtuin 1 comprising residues 140-747 was crystallized using the hanging-drop vapour-diffusion method. The crystal diffracted to 3.4 Å resolution and belonged to space group P622, with unit-cell parameters a = b = 203.1, c = 625.3 Å, and is estimated to contain between six and 12 molecules per asymmetric unit.