Summary—The secondary ion microscope described here allows to obtain the simultaneous registration of chemical and isotopic distribution maps of several elements composing the sample. The instrument has been specially designed to optimize both sensitivity and selectivity: bombardment with primary Cs+ions to increase the ionization yields of negative secondary ions, efficient collection of secondary ions at the target surface, matching of the secondary ion beam etendue with the acceptance of the mass spectrometer working at high mass resolution, spectrometer with parallel detection capabilities. The probe diameter can be made as low as 30 nm and ion induced electron images registered at the same time as ion images. Presently, four ion micrographs are obtained simultaneously over a field of view up to 20 × 20 μm2containing up to 512 × 512 pixels. Examples are shown with an ion probe diameter of 0.