Perfluorocarbons are applied as heavy liquids during vitreoretinal surgery. They are removed again intraoperatively because of possible harmful long-term effects. Following vitreoretinal surgery, residual perfluorodecalin (PFD) was detected in four eyes and localized in two others by fluorine 19 magnetic resonance (19F-MR). In vitro analysis of 19F-MR spectra shows that chemical shift artifacts can be avoided much better with PFD than with perfluorotributylamine and perfluoroctane. Therefore, PFD localization by 19F-MR imaging is superior to that of perfluorotributylamine and perfluoroctane. This examination can be performed on currently employed magnetic resonance imaging systems equipped with a fluorine channel. In the event of significant inadvertent residual quantities of PFD and obscured media, 19F-MR may specifically detect and localize PFD.