We present an innovative wet-chemistry-assisted nanotube-substitution reaction approach for the highly efficient synthesis of boron- and nitrogen-codoped single-walled carbon nanotubes (B(x)C(y)N(z)-SWNTs) in bulk quantities. The as-synthesized ternary system B(x)C(y)N(z)-SWNTs are of high purity and quality and have fairly homogeneous B and N dopant concentrations. Electrical transport measurements on SWNT-network thin-film transistors revealed that the B(x)C(y)N(z)-SWNTs were composed primarily of the semiconducting nanotubes, in contrast to the starting pristine C-SWNTs, which consisted of a heterogeneous mixture of both semiconducting and metallic types.