The complexation of oxacillin to three generations of 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimers was studied with NMR in CD3OD and CDCl3. The stochiometries, which were determined from job plots, were found to be both solvent- and generation-dependent. The dissociation constants (K-d) and Gibbs energies for complexation of oxacillin into the 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimer hosts were determined by H-1 NMR titrations and showed weaker binding of oxacillin upon increasing the size (generation) of the dendrimer.