Poly(ethylene glycol)s (PEGs) in the molecular weight range 200-3400 were derivatized at both ends with acryloyl chloride. These poly(ethylene glycol) diacrylates (PEGDAs) on homopolymerization yield cross-linked networks whose M(c) values should correspond to the molecular weight of the PEGDA macromer. M(c) values calculated according to the Flory-Rehner equation compare very well with the theoretical values for low concentrations of low molecular weight monomers. Those at high concentrations and higher molecular weights are always lower than the expected values. Attempts to resolve the equilibrium swelling and elastic components indicate that the phantom model gives a better fit.