Binary and ternary alloys of molybdenum with iron-group metals were electrodeposited from ammoniacal tartrate baths under galvanostatic conditions. The relationship between the composition of electrodeposited alloys and the cathode current efficiency indicated the two characteristic alloy compositions; the one appeared at a maximum partial current efficiency of molybdenum and the other corresponded to the limiting content of molybdenum. These characteristic alloy compositions were discussed in connection with the mechanism of the induced codeposition of molybdenum based on the electronic structure of the iron-group metals.