Gentamycin (GS) is administered as intravenous or intramuscular solution because of its poor oral bioavailability. However, the intravenous administration associated with pain and needs some skills. In this study, five nonionic microemulsions (MEs) for oral and transdermal application were developed using nonionic surfactants. The MEs were characterized for their droplets sizes, rheological properties. Furthermore, the transdermal was evaluated by estimation the flux and permeability coefficient through rat's skin using Franz diffusion cell. The results show that the MEs complied with the colloidal properties. The ME with highest flux of 1.892 mg/cm2*h of these formulations was chosen for further oral bioavailability in rats in comparison to an aqueous solution of GS. The ME showed a percentage relative bioavailability of 239.7 % in comparison to an oral solution.