Cryptosporidium is an intestinal protozoan parasite which causes diarrhoea in animals and has recently been reported to cause similar symptoms in man. Cryptosporidiosis is a zoonotic infection and the first human case was reported in 1976.2 Since then the number of cases has increased by the hundreds especially among patients with acquired immuno-deficiency syndrome (AIDS), as a result of the severe symptoms that they cause in the im-munosuppressed patients and also due to the better screening techniques which have been developed resulting in the detection of cases.3 To date 20 species of Cryptosporidium have been reported but these cannot be differentiated morphologically. The differences are based mainly on the host from which the parasites were recovered. The species responsible for causing infection in man is Cryptosporidium parvum.4 Of the 20 species reported several are invalid because the oocysts of some of them were found to be the same as the sporocyst of Sarcocystis. It is now concluded that there are only two species that infect mammals (C. Muris and C. parvum). (Copied from article).