Background: The uncertainty is innate in parents of children under bone marrow trasplantation. The parents' view of uncertainty during their children's bone marrow transplantation (TCSE) hasn't yet been explored. There is evidence that uncertainty experienced as a reaction to disease is linked to a lower quality of life. The purpose of this study was to explore the parents' experience of uncertainty during their children's TCSE. Methods: This study applied qualitative approach using phenomenology method. To perform this qualitative study, semistructured interviews were performed. Basing on this analysis, we will evaluate if Mishel's Uncertainty in Illness Theory can explain this experience and specify the connection between uncertainty experienced by family and nursing care during TCSE. A convenience sample of 26 parents were recruited from TCSE unit in Padua Hospital. Each interview was audio recorded, transcribed, and coded for major theme using a content analysis approach. The extracted interviews were analyzed through Colaizzi method. Interview topics were: uncertainty aspects during bone marrow transplantation, means of uncertainty, life aspects influenced by uncertainty, how dealt with uncertainty. Results: From the analysis of the interviews four macro categories were defined: multiple uncertainty's meanings, multiple side of uncertainty, uncertainty side effects, management of uncertainty. The parents will live the consequences of such uncertainty for all their life and they will never find a boundary which lay the end. The bone marrow transplantation doesn't remove uncertainty, but it causes uncertainty. Parents report need for contact with expert nurses to discuss the meaning of their uncertainty, in order to reduce it. Conclusions: The parents' experience of uncertainty can be described following Mishel's Uncertainty in Illness Theory. The lives of the parents are dominated by uncertainty. Nurses need to be educated to be able to encourage parents to communicate their existential questions and the impact of the illness on their life. Enhanced awareness and increased understanding about parents' uncertainty can be important factors in improving nursing work environment and the quality of care presented to pediatric patients and their family.