Progress in stereospecific living polymerizations of methacrylate monomers and the concept and realization of "uniform polymers" and "uniform polymer architectures" are described, with particular emphasis on the fusion of polymer synthesis and characterization and their interactive stimulation, which are inevitable not only for the formation of polymers with highly controlled structures but also for the development of polymer characterization, thereby bringing about the spiral progress of both fields. First, three types of stereospecific living polymerizations are described, including formation of 100% isotactic poly(methyl methacrylate) (PMMA), 98% syndiotactic PMMA, and 96% heterotactic PMMA. Supercritical fluid chromatography (SFC) has proven useful for isolating uniform polymers from these stereoregular PMMAs with narrow molecular weight distributions. Living nature of these stereospecific polymerizations is further utilized for the synthesis of end-functionalized stereoregular polymers, which are separated into uniform end-functionalized polymers and used to construct more elaborated uniform polymer architectures such as stereoblock, star, and comb polymers. The uniform polymers have proven quite useful for the studies on the relationship between structures and properties such as glass transition temperature, melting temperature, and solution viscosity. In addition to this, stereoregular uniform polymers are particularly important to understand stereocomplex formation between isotactic and syndiotactic uniform PMMAs. On-line GPC/NMR measurement at 750 MHz and -15 degrees C in acetone/acetone-d(6) allowed definitive determination of the compositions of the complexed species and noncomplexed species separately, but not in average. Also interesting is the stereocomplex formation of uniform stereoblock PMMA, where intramolecular complexation in addition to an intermolecular complexation was distinctively observed by GPC analysis in acetone. Uniform star and comb PMMAs were also prepared and found useful to discuss the effect of branching on the solution viscosity.