The purpose of this research was to evaluate in vitro transnasal sustained-release ability of sorbitan monostearate (SMS) organogels in isopropyl myristate (IM). Organogels were prepared containing SMS (2.5%-20%) and water (5%-25%) in IM and analyzed microscopically for phase behavior. The effect of Tween surfactants on gel strength and in vitro nasal diffusion of propranolol is reported. The in vitro nasal release retardant effect of SMS and Tween 20 was investigated using factorial design. The microscopic changes in structure of organogel during in vitro nasal diffusion were studied. The water-holding capacity of SMS organogels in IM increased with SMS concentration. The release retardant effect with incorporation of cosurfactant was of the order of Tween 80 > Tween 60 > Tween 20. Gel strengthening and increased viscosity were evident with increased concentration of SMS and Tween 20. The 3-dimensional network of SMS molecules controls the diffusional drug release. The organogel system on nasal mucosa during diffusion is dynamic in nature and changes continuously with the time of diffusion. The water penetration in the organogel network results in percolation and emulsification of organogel, thus affecting the release. Organogels provided an effective barrier for diffusion of propranolol. The surface epithelium lining and the granular cellular structure of treated nasal mucosa were intact.