Enzymes are environmentally friendly, non-toxic catalysts that have found many applications in synthetic polymer chemistry. However, until very recently no examples of enzyme-catalyzed, controlled radical polymerizations were known. Here we review the nascent field of biocatalytic atom transfer radical polymerization (ATRP). The heme proteins horseradish peroxidase, hemoglobin and catalase, as well as the copper-containing enzyme laccase have been reported to display catalytic activity in activators regenerated by electron transfer (ARGET) ATRP of two model monomers, N-isopropylacrylamide and poly(ethylene glycol) methyl ether acrylate. Bromine-terminated polymers, low polydispersity indices, linear increase in molecular weight with conversion as well as first-order kinetics indicate ATRP-type mechanisms. However, the first examples of biocatalytic ATRP also show that enzymes are much more complex catalysts than conventional ones.