To easily perform atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in homogeneous medium from unprotected polysaccharidic macroinitiators, the ATRP of MMA carried out in dimethylsulfoxide has been firstly reinvestigated using Cu(I)Br as metal catalyst and ethyl 2-bromoisobutyrate as initiator. Two ligands, 2,2'-bipyridyne (Bpy) and N-(n-propyl)-2-pyridylmethanimine (n-Pr-PMI), have been compared, as well as the addition of Cu(II)Br(2) (10 molar % relative to Cu(I)Br) or the adjustment of experimental temperature (from 30 to 60 A degrees C). Appropriate conditions were founded for both ligands to achieve a controlled ATRP. Bpy giving far much faster polymerization compared to n-Pr-PMI, n-Pr-MI was preferred as ligand for accurate tuning of the conversion. Experimental procedure was then applied to unprotected macroinitiators based on dextran to obtain amphiphilic poly(methyl methacrylate) grafted dextran. While homopolymerization was controlled in these conditions, parameters have to be adjusted for the hydrophilic unprotected macroinitiators to prevent gel formation and control ATRP.