The properties of amorphous Fe-B-C alloys have been studied. The replacement of boron by carbon reduces the thermal stability of alloys containing more than approximately 80-percent iron, increases the Curie temperature slightly, and decreases the slope of the magnetization-temperature curve. Thus, although the low-temperature saturation magnetization decreases on replacement of B by C, as expected, the room-temperature magnetization exhibits a broad ridge of constant saturation magnetization per gram extending from approximately Fe80B20to approximately Fe83B11C6. This ridge follows one of the low-temperature magnetization contours. The density of the alloys in the series Fe84B16-xCxwas measured and compared to calculated densities. The increase in density agrees with the calculated values and results in a slight increase in saturation magnetization per unit volume with increase in carbon. The coercivity, both as-cast and after stress relief annealing, increases on replacement of B by C. This is not understood.