Osteopetrosis, a rare condition caused by a failure of osteoclasts to resorb bone, results in dense and deformed bones, growth failure, anemia, hypoplastic dentition, chronic infection, blindness, and massive splenomegaly. Children with infantile osteopetrosis have disease-related complications that affect nutritional status. Altered calcium and phosphorus intake has been reported in these patients, but previous studies did not include an assessment of dietary adequacy or nutrition-related complications. A prospective study of six children with severe infantile osteopetrosis was conducted to identify specific nutrition-related problems and effective nutrition intervention strategies. Patients were monitored by a registered dietitian while they participated in a clinical research protocol at St Jude Children's Research Hospital. Dietary records for each patient were obtained at set intervals during the 4-month study period. Because most patients lacked adequate dentition, they had difficulty obtaining adequate nutrition through normal oral intake. Three children required nutrition supplementation (enteral feedings for one and oral supplements for two). We conclude that oral and enteral nutrition support can provide nutrients needed for improved growth and response to treatment in patients with osteopetrosis.