The high-frequency magnetic properties of an Fe-B-Si amorphous alloy have been improved and made reproducible by the addition of chromium and carbon. Controlled crystallization of α-Fe has been demonstrated to be primarily responsible for optimum high-frequency properties in Fe-base amorphous alloys. However, oxidation of metalloids on the ribbon surfaces introduces variabilities in crystallization of α-Fe in the metalloid-depleted areas. Consequently, variability in core losses occurs. The prevention of metalloid oxidation at the ribbon surface is expected to enhance reproducibility. Addition of chromium was found to develop a protective layer of chromium oxide on the ribbon surface minimizing surface oxidation of metalloids. The chromium oxide layer increases the interlaminar resistance and is expected to reduce eddy current losses. Addition of chromium also reduces saturation magnetostriction (λs). The effect of small additions of carbon on the Fe-B-Si-Cr system was also evaluated. Carbon additions were found to enhance and control the formation of α-Fe crystallites. The resulting high-frequency core losses were found to be routinely reproducible and appreciably lower than the Permalloys. Detailed high-frequency properties of the Fe-B-Si-Cr-C system are discussed.