The stability and electronic properties of compositeBxCyNznanotube heterojunctions were studied using bothab initioand semi-empirical approaches. C/BN andBC2N/BNsuperlattices or isolated junctions were investigated as specific examples of the wide variety of electronic devices that can be realized using such nanotubes. The characteristics of these junctions are predicted to be largely independent of the radius, helicity, multiplicity, or degree of perfection of the constituting nanotubes. ©1997 American Institute of Physics.