The ternary diagram of the amorphous phase in the splat-cooled Fe--P--B system was investigated by x-ray diffraction measurements. Alloys were found to be amorphous within the Fe concentration range 75 less than or equal to c/sub Fe/ less than or equal to 83 at. percent. For a fixed Fe concentration, B substitutes for P over a large scale, the maximum substitution occurring for c/sub Fe/ = 80 at. percent. Concentration dependence of the electronic and magnetic properties was systematically studied in alloys within the whole amorphous diagram by means of bulk magnetization, anti .mu. (4.2/sup 0/K), Curie temperature, T/sub c/, and electrical resistivity, rho, measurements from 4.2/sup 0/K up to the amorphous-crystal transformation. The composition dependence of anti .mu. and T/sub c/ when B substitutes for P at c/sub Fe/ constant suggests the existence of two different short-range orders in the amorphous alloys, corresponding to the epsilon and epsilon/sub 1/ crystal structures in the Fe/sub 3/P/sub 1-x/B/sub x/ compounds. The concentration dependence of anti .mu. and T/sub c/ when P (or B) substitutes for Fe at c/sub B/ (or c/sub P/) constant is explained by a comparison between the amorphous Fe and the fcc Fe. A minimum in the variation of rho as a function of the temperature T occurs at T/sub m/. The temperature dependence of rho is expressed by a phenomenological law: rho(T) = rho/sub 0/ + A log T + B T/sup 2/ + CT. The concentration dependence of T/sub m/ and of the coefficients A and B is discussed in relation with the magnetic and structural properties of the amorphous Fe--P--B alloys. 10 figures, 1 table.