Semiconductor nanowires are very promising for future technology. A relationship between the diffusivity D-C and the mobility mu(C) of semiconductor nanowires has been presented. Calculations have been performed to elucidate the dependence of D-C/mu(C) on the carrier concentration n and the temperature T. The D-C/mu(C) relationship appears to be general enough for application to both nondegenerate and degenerate semiconductor nanowires under an applied bias. An analytical form for this D-C/mu(C) relationship based on one-dimensional dispersion formula and a reasonable approximation to the Fermi-Dirac integral is suitable for investigation of electrical transport in semiconductor nanowires. (C) 2008 American Vacuum Society.