The optical and magneto-optical properties of Mn1-xFex alloy films were investigated. The equatorial-Kerr-effect (EKE) signal at 293 K could be observed only for x>0.50. All the EKE spectra have nearly the same spectral shape and differ from each other only in the magnitude. The optical properties can be categorized into three groups which are related to different crystalline structures; predominantly alpha-Fe for 0.8 < x < 0.97, gamma-Mn-Fe for 0.2 < x < 0.6, and predominantly alpha-Mn for 0.02 < x < 0.23. (C) 2004 Elsevier B.V. All rights reserved.