The aim of this diploma thesis was to develop a nanoemulsion of O/W type stabilized by nonionic and ionic surfactant and polyelectrolyte. Nanoemulsions of O/W type were prepared using the high energy method of microfluidisation with Miglyol 812 as the oily dispersed phase. The prepared nanoemulsions were subjected to measurments of thier average droplet size, polydispersity index and zeta potential depending on the rising mass fraction of lecithin S45, Cremophor EL and low, as well as medium molecular weight chitosan. The final nanoemulsions with the best properties and stability were formulations containing 2,5% Miglyol 812, 0,05% lecithin S45, 0,25% Cremophor EL and 0,05% low and 0,1% medium molecular weight chitosan respectively. By increasing the fraction of lecithin and Cremophor EL, droplet size of the system decreases, while, on the contrary, increasing the fraction of chitosan results in bigger droplets. The values of the polydispersity index did not show dependence on the lecithin share, while the growing share of Cremophor EL and chitosan generally increases the PDI values. Zeta potential gets more and more negative with the increase of lecithin share, but by adding Cremophor EL that negative zeta potential diminishes and approaches zero. The addition of chitosan sees the shift of zeta potential into positive values that grow with an increasing share of chitosan. All of the developmental formulations containing lecithin and Cremophor EL expressed stability thirty days after their preparation. The final nanoemulsions with low molecular weight chitosan share of 0,1% and above and medium molecular weight chitosan share of 0,2% and above were found to be not stable enough during the same period of thirty days. Comparison of the results of average droplet size, polydispersity index and zeta potential measurments between low and medium molecular weight chitosan nanoemulsions did not show significant differences in the values of these parameters.