A self‐consistent‐field, near‐Hartree‐Fock method is applied to study the structure and stability of B4C. Hydrogens serve as bond tie‐offs. Consideration of a large variety of B12C2H16 cluster configurations reveals that one C is highly favored over 0, 2, or 3 in the icosahedron. The C‐B‐C chain is highly favored over all other chains. C’s as far apart as possible are favored, as are C s in triangle positions. The combination of a B11C icosahedron (C in a polar triangle position) with a C‐B‐C chain is the lowest in energy. Geometric optimization is used for the two most‐stable conformations. Two‐icosahedron clusters are also investigated.