Four EBE copolymers (E = oxyethylene repeat unit, B = oxybutylene repeat unit) based on a B-20 central block and end blocks ranging from 58 to 260 E units were studied. Rheological measurements (oscillatory and steady shear) were used to confirm gel boundaries (previously explored by a tube inversion method) and to determine storage and loss moduli (G ' and G ") and yield stresses (sigma (y)) for aqueous gels formed at copolymer concentrations below 20 wt %. The phase diagrams contained a region of hard gel (G ' > G ", high G ' and sigma (y)), an extensive region of soft gel ((G ' > G ", low G ' and sigma (y)), denoted 1, and a second region of soft gel at low temperatures, denoted 2. Small-angle X-ray scattering was used to probe the hard gel structure. Concentrated aqueous gels (20 wt %) had a body-centered cubic (bcc, Im (3) over barm) structure. The structure of dilute gels near to the hard gel boundary was not defined, although the Im (3) over barm and Pm (3) over barm cubic structures were eliminated. Depending on concentration, the soft gels were assigned either to percolation-induced fractal structures (soft gel 1) or to defective cubic structures (soft gels 1 and 2).