A slightly crosslinked sample of atactic poly(methyl methacrylate) was used to determine the solubility parameters from gravimetric sorption tests made at 40 degrees C with about 30 solvents of solubility parameter ranging from 17.2 to 47.4 MPa1/2. It was shown that solubility spectra of this sample and a linear homopolymer do not differ significantly. Classical methods of unidimensional or bidimensional mapping failed to determine precisely and unambiguously the solubility parameters of the polymer. The best approach consisted of distinguishing between three solvent families, respectively, poorly, moderately and strongly hydrogen bonded, as proposed by Burrell. The maximum capacity of solvent absorption varies in the order poorly > moderately > strongly hydrogen bonded solvent, which was tentatively explained by the importance of the plasticizing efficiency of the solvents. This provides an explanation of the difference between the solubility parameter value determined from solvent sorption tests (19-21.5 MPa1/2) and from ultrasonic measurement of the bulk modulus (23 MPa1/2).