This study demonstrates that the molecular weight of polyalkylcyanoacrylate nanoparticles can be modified by the composition of the polymerization medium, the nature of the monomers and the drug to be linked to the carrier. The influence of a surfactive agent is particularly important because polymers of very high molecular weight have been obtained. Likewise, polyalkylcyanoacrylate molecular weight distribution has been greatly modified after binding doxorubicin to nanoparticles. These long polymers could induce important changes in carrier degradation, in bound drug bioavailability and in polymer excretion rate. Some additional findings have been added concerning the state of polyalkylcyanoacrylate polymer during the degradation process.