Malignant histiocytosis is a rare form of cancer in children and adults. Until recently almost all persons diagnosed with this form of malignant disease died within months. The focus of this article is on the pediatric nursing implications of diagnosis, chemotherapy, support services, and parental involvement. Two case histories are utilized in describing the nursing implications of this acute life-threatening illness. One patient diagnosed at age 3 1/2 is currently doing well after his 7th birthday; another patient diagnosed at age 2 had a much different outcome. The description of each presentation, diagnosis, and treatment regimen brings issues into focus applicable to other life-threatening diseases.