F4 (formerly K88) fimbriae from enterotoxigenic Escherichia coli are assembled via the FaeE/FaeD chaperone/usher pathway. The chaperone FaeE crystallizes in three crystal forms, all belonging to space group C2. Crystals of form 1 diffract to 2.3 A and have unit-cell parameters a = 195.7, b = 78.5, c = 184.6 A, beta = 102.2 degrees. X-ray data for crystal form 2 were collected to 2.7 A using an SeMet variant of FaeE. The crystals have unit-cell parameters a = 136.4, b = 75.7, c = 69.4 A, beta = 92.8 degrees. Crystals of form 3 were formed in a solution containing the FaeE-FaeG complex and diffract to 2.8 A. Unit-cell parameters are a = 109.7, b = 78.6, c = 87.8 A, beta = 96.4 degrees.