Phosphoglucose isomerase (PGI) is a key enzyme in glycolysis and glycogenesis that catalyses the interconversion of glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P). For crystallographic studies, PGI from the human malaria parasite Plasmodium falciparum (PfPGI) was overproduced in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data to 1.5 A resolution were collected from an orthorhombic crystal form belonging to space group P2(1)2(1)2(1) with unit-cell parameters a = 103.3, b = 104.1, c = 114.6 A. Structural analysis by molecular replacement is in progress.