We have investigated the structural and electronic characteristics of single-walled nanotubes composed of group 15 elements P, As, Sb, and Bi. Systematic quantum chemical studies on the elemental nanostructures were performed to obtain periodic trends for their stabilities, structural principles, and electronic properties. By studying P, As, Sb, and Bi nanotubes up to 5.4, 5.0, 5.7, and 6.0 nm in diameter, respectively, we found their structures and stabilities to converge smoothly toward their experimental bulk counterparts. A rhombohedral structural model was found to be favored over ail orthorhombic one for all the elements, but in accordance with the experimental characteristics of the elements also the orthorhombic model was found to be important for phosphorus. All studied group 15 nanotubes were found to be semiconducting.