Microemulsions with timolol as potential eye-drops - study on changes of formulations physical parameters. Stable microemulsions oil-in-water [o/w] and water-in-oil [w/o] with timolol were obtained. These formulations were sterilized using two methods: by autoclaving and by sterile filtering according to FP V. Microemulsions were kept in the temperatures of 25°C and 5°C during one year. The following physical parameters were investigated: density, dynamic viscosity, refractive index, surface tension, pH and osmotic tension. All the microemulsions met the requirements for eye drops.