Possible mammographic advantages in diagnosing human breast cancer of trans-Mo anodes (atomic number > 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 [half value thickness] in Al, and penetration in lucite were measured spectroscopically for an experimental Rh-anode tube and also for Mo- and W-anode mammographic tubes. The trans-Mo tube had 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.