e20625 Background: When a child is diagnosed with cancer, the entire family is affected. In qualitative studies, 28–81% of siblings of children with cancer display behavioral maladjustment. Quantitative studies show similar findings, documenting up to a three-fold increase in clinically significant behavioral problems among siblings of children with cancer. Methods: In order to better understand sibling distress we conducted 3–4 interviews using grounded theory methodology (a qualitative strategy to explore common themes and develop theory) with each family member over 9 years old of 7 families with a child undergoing a sibling donor bone marrow transplant for cancer or sickle cell anemia. Participants also completed standardized scales related to coping. Results: Of the 29 subjects interviewed, 6 were African American, 4 Hispanic and 19 white. Six parents had at least a college degree and income was evenly distributed from $5,000 to >$80,000 a year. Children, including 4 patients, 6 donor siblings and 5 other siblings, ranged in age from 9 to 18. Based on the grounded theory analysis of each interview, we theorize that siblings experience less distress if the parents share the patient care giving. Our data support this hypothesis, with analysis of interviews indicating improved coping in families that shared care giving for the transplant recipient, and increased distress in families in which all the patient care giving was performed by the mother, a commonly used strategy. Conclusion: In order to potentially facilitate increased family functioning and decrease caregiver burden, parents should be encouraged to share care giving when feasible. Our study shows that systematic interviews can explore the family experience of pediatric transplantation and allow development of improved support systems for families of children undergoing sibling donor bone marrow transplantation. No significant financial relationships to disclose.