The diagnosis and treatment of moderate-to-severe diarrhea in solid organ transplant recipients is often a challenge because of the variety of infectious and non-infectious causes. The morbidity associated with this clinical condition is of particular significance in the pediatric population where malnutrition may lead to poor growth and development. Rarely, Cryptosporidium has been identified as the cause of clinically significant diarrhea in pediatric solid organ transplant patients. A retrospective review identified cases of cryptosporidiosis among the 1160 non-renal, abdominal organ transplant recipients cared for at the Children's Hospital of Pittsburgh between 1981 and June 1998. Four cases of clinically significant diarrhea were identified in three liver transplant recipients and one small bowel transplant recipient. Endoscopy and biopsy with histologic confirmation diagnosed three cases; ova and parasitic examination of stool specimens identified the fourth case. Therapy varied among the patients depending on when they had been diagnosed as, over the years, different and newer agents have been indicated for the treatment of cryptosporidiosis. All four patients resolved their infections. Hence, endoscopy and biopsy is recommended for pediatric transplant patients who present with chronic diarrhea of unknown etiology. The patients who may be at a higher risk for cryptosporidial infections include those with an increased immunosuppressive state (i.e. pre-existing immunodeficiency, malignancy, re-transplantation, and those receiving higher doses of immunosuppressive therapy). While cryptosporidiosis is a non-lethal complication, it allows the clinician to gain further insight into the degree of immunosuppression of their patient.