Uncertainty has been described as one of the major stressors faced by children with cancer and their families. However, ill children's responses to uncertainty have not been systematically studied. This grounded theory study of 11 children undergoing treatment for cancer confirmed that children experience multiple uncertainties in the context of cancer diagnosis and treatment. For the most part, however, children did not characterize themselves as feeling uncertain. Instead, they quickly came to view their lives as routine and ordinary despite the unpredictable nature of their illness course. Children described a process of getting used to cancer that allowed them to keep their focus on the ordinary nature of their everyday lives within the uncertain context of their illness. This interplay between uncertainty and routine provides important insight into children's psychological adjustment to life-threatening illness.