The three Independent elastic constants of the bcc niobium structure have been determined as a function of temperature over the range 4.2°-300°K, using an ultrasonic pulse technique - the propagation of 10 Me waves in preferred directions in the crystal specimen. Values obtained at 4.2°K are, in units of 10 dyne/cm2, c11 = 25.27 +/- 0.6%, c44 = 3.10 +/- 0.6%, c12 = 13.32 +/- 3.3%. A few measurements were also carried out on the thermal expansion of niobium, from 140°-280°K, and this quantity determined at a function of the temperature. The average expansion coefficient over the whole range studied was 6.24x10 to the -6th deg -1, which agreed moderately well with earlier work by other investigators.