Mucoromycetes are well-known cosmopolitan molds. Recently, these fungi have become increasingly important due to their ability to cause life-threatening infections in immunocompromised persons. This paper is the first one to study the ultrastructure of hyphae and sporangiospores in Rhizomucor pusillus, using the strain RCPF 1845. Species identification was done by morphological analysis and confirmed by DNA sequencing of the large subunit ribosomal RNA gene. For a more comprehensive analysis, transmission electron microscopy was carried out with specimens, fixed by chemical and cryofixation with high pressure freezing procedure. High pressure cryofixation preserved microtubules in the cytoplasm and nucleoplasm better, although traditional chemical fixation using paraform allowed to get the acceptable images of sporangiospores. We described the structure of nuclei, cell walls and septa, mitochondria and autophagic vacuoles. New data have been obtained on the vesicular transport through the hyphal wall.