Cryptosporidiosis is a parasitic disease result from parasite Cryptosporidium parvum, that effect intestinal tract of mammals. It was recorded that this parasite causes 6% of diarrhea in immunocompetent persons and 24% in AIDS persons. The primary symptoms of this disease are non- bloody and watery diarrhea, also may cause abdominal pain, nausea, vomiting, and anorexia, .Infection can affect other organs such as gall bladder, liver, and lungs. The aims of this review article to provide the important update information of Cryptosporidium parasite, which is the causative agent of cryptosporidiosis. In conclusion cryptosporidiosis is considered a serious health problem, infect human intestinal tract of different ages, and children are the most cases of this disease which have severe pathologic signs.