A burner configuration that allows the creation of nearly unstretched one-dimensional diffusion flames has recently been introduced. This paper presents the first detailed characterization of flames produced in such a burner to assess how well they approach the idealized one-dimensional configuration, which is used extensively for the development of theoretical models for diffusion flame stability. Particular emphasis is directed at quantifying the remaining inhomogeneities in the burner, such as residual flame stretch or variations in the boundary conditions, and identifying possible means to minimize them. Measurements made include the velocity field, stable species concentration profiles and temperature distribution throughout the burning chamber. Additionally, the flame position in the burner is determined as a function of mixture strength, reactant transport properties and bulk flow velocity. All the measurements are found to be in good agreement with a simplified one-dimensional flame model. However, the boundary conditions and their physical location have to be determined experimentally on both sides of the flame, which complicates comparison with results from theoretical and numerical models. Despite these limitations, we conclude that this new burner type provides a good experimental approximation of the one-dimensional idealized construct. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.