The purpose of this study was to determine whether blood counts discriminate between sickle cell pain episodes that lead to successful discharge from the emergency department (ED) and those that result in complications. This retrospective review compared the hemoglobin, reticulocyte count, and white blood cell count with differential during complicated and uncomplicated ED visits. Complicated visits were pain episodes followed by admission, by readmission within 48 hours, by acute chest syndrome, by an aplastic crisis, or by the administration of blood or antibiotics. There were 2 statistically important differences between complicated and uncomplicated pain episodes. Children successfully discharged were younger than those experiencing a complicated visit (8.9 v 11.2, P = 0.04). At a difference of 0.4 g/dL, the change in hemoglobin from baseline among children with complicated versus uncomplicated pain crises was not clinically useful. Routinely performed blood counts do not reliably identify the course of sickle cell pain crises.