Abstract The main goal of the KLOE experiment is the study of CP violation in the K mesons system, with an accuracy of 10 −4 in the measurement of Re( ε′ ε ) . This task imposes strong constraints on the design and operation of the drift chamber, which must reconstruct the charged decays of low momentum K L's and K S's with high efficiency and high resolution. A full-length prototype of the chamber has been built and tested on a 50 GeV/ c beam. The analysis of the large sample of data has allowed a detailed study of the time to distance relations as a function of the track parameters and of the peculiar geometry of the drift cell. The detector performance, in terms of efficiency, spatial resolutions and dE dχ resolution, is illustrated and discussed.