The combination of electron beam scanning and X-ray detection allows to use the scanning electron probe microanalyzer as a sensitive microscope to elemental constitution. This made it possible to investigate three species of the Aspergillus nidulans group: A. nidulans, A. unguis, A. variecolor. Qualitative differences were found between the three species. The application of microanalysis is regarded as a useful addition to more conventional methods used in histochemical studies. The advantages of examining specimens which have not been submitted to fixation, dehydration and embedding are briefly discussed.