We evaluated the ultrasound biomicroscopy findings and the amount and location of silicone oil residue in anterior structures of the eye before and after silicone oil removal. We examined the anterior structures in 40 silicone oil 1000 cs-filled eyes at the end of silicone oil tamponade time (mean silicone oil tamponade duration 5.1 months), and in the same eyes after silicone oil removal. High resolution ultrasound biomicroscopy, 50 MHz transducer, 50 microns of resolution, was used. Silicone oil droplets--often not ophthalmoscopically visible--appeared as highly reflective images with after ringing effect. They were present in the anterior structures of the eye in up to 95% of eyes with silicone oil in the vitreous cavity, and in up to 87.5% after careful silicone oil removal. With ultrasound biomicroscopy it was possible to identify small silicone oil droplets with a typical morphological appearance. Once silicone oil is used in vitreoretinal surgery, its complete removal from the anterior structures of the eye is very difficult to achieve later on.