The biological diagnosis of human cryptosporidiosis is made primarily by identifying Cryptosporidium oocysts in stool specimens under the microscope. It is advisable to fix and stain the fecal smears by the technique according to Henriksen. It is possible to examine fresh specimens and to carry out concentration techniques but this requires excellent knowledge of the cytology of the parasite. Cryptosporidium can also be identified from intestinal biopsies.