The spatial profiles of fluid flow velocity in transparent glass and turbid collagen conduits are measured by optical Doppler tomography (ODT). The flow velocity at a discrete user-specified spatial location in the conduit is determined by measurement of the Doppler shift of backscattered light from microspheres suspended in the flowing fluid. Experimental data and theoretical calculations are in excellent agreement. ODT is an accurate method for the characterization of high-resolution fluid flow velocity.