[en] Charge symmetry breaking in np elastic scattering at 347 MeV has been measured with high precision. From fits of the measured asymmetry curves over the angular range 53.4 degrees <- θ cm <- 86.9 degrees, the difference in the center-of- mass zero-crossing angles of the analyzing powers was determined to be 0.438 degrees ± 0.054 degrees (stat.)± 0.051 degrees(syst.). Using the experimentally determined slope of the analyzing power, dΑ/dθ = (?1.35± 0.05) x 10^-2 deg^-1 , this is equivalent to Ε ΑA = [ 59 ± 7(stat.) ± 7(syst.) ± 2(syst.)] x 10^-4. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with this result. (author)