Uniform oligomers are special polymers with no molecular weight distribution. We separated uniform oligomers from commercial monodisperse samples by preparative super-critical fluid chromatography. Using equimolar mixtures of uniform oligomers, we showed it possible to evaluate the quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for analysis of molecular weight distribution of a monodisperse polymer sample. Uniform oligomers are also useful to know exact values of physical properties of polymers. We measured their diffusion coefficients and radii of gyration in dilute aqueous solutions and have shown clear molecular weight dependence of these properties.