Recent progress on polymerization of diazoacetates is described. Polymerization of diazoacetates has attracted much attention as an efficient method for C1 polymerization, which constructs C-C main chains from one carbon units. A variety of initiating systems consisting of Cu, Pd, B, and microwave activation have been revealed to afford polymers from diazoacetates with relatively low molecular weight. Rh-initiated polymerization of diazoacetates is remarkable for its ability of affording high molecular weight polymers in a stereospecific manner. The essence of the active species and mechanistic details for the Rh-initiated polymerization have been clarified by a combination of experimental and theoretical investigations. Copolymerization of diazoacetate with (CH2)(n)-affording monomers yielded unique polymer structures comparable to those of ethylene-acrylate copolymers. A series of postpolymerization modification approaches have been examined for the polymers obtained by the Rh-initiated polymerization. Some Pd-based initiating systems have been revealed to be effective for the polymerization of diazoacetates. A variety of substituents were introduced as ester substituents of diazoacetates, and they were polymerized by the Pd-based initiating systems. The effect of dense packing of the substituents on properties of the resulting polymers were examined in comparison to their vinyl polymer counterparts, and the enhanced properties in poly(substituted methylene)s were indeed observed in a number of examples.