A set of experiments is described that obtain the shape of stable, straight, uniform, mobile-bed channels with cohesionless banks. These experiments were carried out in an outdoor flume at length scales at least twice those used by previous experimenters, but otherwise using similar techniques, including the use of a half channel against the flume wall in order to suppress meandering. Eight flume runs are reported, including channels farther from threshold conditions than those previously tested. The resulting data might prove useful both in validating theories for the stable shape of the straight channel and for advancing models of the adjustment to that shape. ¿ 1999 American Geophysical Union