The structure of end-linked poly(tetrahydrofuran) networks was investigated by equilibrium swelling and small-angle neutron-scattering (SANS) experiments. The end-linked poly(tetrahydrofuran) networks were prepared by a reaction of telechelic poly(tetrahydrofuran) having - C = C group at both ends with a four-functional cross-linking reagent having - SH groups, where the molar ratio, r, defined by [- SH]/[ - C = C] was varied. The molar ratio, r, dependence of the polymer volume fraction at the swelling equilibrium showed a maximum for each network prepared from prepolymers having different number-average molecular weights, M(n). The molar ratio giving the maximum, r(m), increased linearly with M(n), which results from a competition between ideal cross-linking formation with the functionality, f, being 4 and defect formation with f < 4, such as three- or two-functional cross-linking and end-capping by crosslinker. The SANS profiles from gels at swelling equilibrium were analyzed with a combination of two types of scattering functions, representing static (solid-like) and solution-like fluctuations. A master relationship was found between these structure parameters and the equilibrium volume fraction, phi, which was the same as that for the networks prepared at the stoichiometric condition.