The unique physicochemical properties of nanoparticles make them promising substrates for application in the medical area. As there are no safety regulations yet, concerns about future health problems are rising. This study was conducted to prepare approximately 20 nm gold nanoparticles (GNPs) by a chemical reduction method and evaluate their cytotoxicity by MTT assay using human dermal fibroblasts-fetal (HDF-f). 10-50 nm GNPs could be obtained in redistilled water by varying the amount of sodium citrate. MTT results showed that approximately 20 nm GNPs did not cause cell death at a maximum concentration of 300 microM but affected the morphology of HDF-f when their concentration increased.