Possible mammographic advantages of "trans-molybdenum" anodes (atomic number greater than ZMo) are decreased dose because the fluorescent radiation is more penetrating, and increased useful output; contrast degradation is known to be tolerable. The output per mAs, the HVT in Al, and the penetration in Lucite were measured spectroscopically for an experimental Rh-anode tube and also for Mo- and W-anode mammographic tubes. The trans-molybdenum tube was shown to have output and dose advantages over Mo anodes, and output and contrast advantages over normal and selectively filtered W anodes. Possible applications in areas other than mammography are briefly discussed.