The anisotropy between longitudinal and transverse magnetoresistance has been measured in a number of amorphous Fe90-xMnxZr10 (x=0-12) alloys in fields up to 50 kOe at various temperatures between 4.2 and 300 K. The observed composition dependence of the spontaneous resistivity anisotropy can straightforwardly be explained in terms of the two-current-conduction model. The composition dependence of spin-up and spin-down residual resistivity has been determined, and provides conclusive evidence of weak-itinerant ferromagnetism in the entire range of compositions of the present investigation. These observations are further supported by high-field susceptibility data obtained from magnetization measurements. (C) 2003 American Institute of Physics.