[en] Nanotechnology is a broad and interdisciplinary area of research that has been an important increase in recent years. Among the various types of nanomaterials studied stand out in particular the gold nanoparticles (AuNPs) which can be applied in several fields such as biotechnology and biomedicine. The interest in development of AuNPs is due to its extraordinary physical and chemical properties resulting from the nanoscale. In this work it was developed a new process to obtain biocompatible AuNPs, whose surface was modified to allow its subsequent association to drugs with antitumor activity. Were obtained AuNPs modified with thiols, which allowed conjugation of the polymer polyethylene glycol (PEG). The results indicate the formation of AuNPs stabilized by citrate ion, with sizes ranging 5-10 nm and strong absorption at 520 nm. Nanoparticles modified with thiol and PEG showed sizes of 62 nm and 644 nm, respectively, and had easy redispersion in water. The concentration of nanoparticles in each solution was determined by neutron activation analysis. author)