To evaluate the relative severity of acute vs chronic salicylate poisoning in children, 112 cases (65 acute and 47 chronic) of salicylate poisoning (salicylate concentration greater than or equal to 20 mg/100 ml) admitted to The Children's Hospital Medical Center in Boston and Primary Children's Medical Center in Salt Lake City between the years 1967 and 1978 were analyzed. Hyperventilation (P less than .01), dehydration (P less than .001), and severe central nervous system manifestations (P less than .001) occurred more frequently in the chronic group and remained more frequent (P less than .01) when patients having disease states capable of producing these signs and symptoms were removed from statistical analysis. At three separate salicylate concentration ranges (20 to 39, 40 to 59, and greater than or equal to 60 mg/100 ml) hyperventilation, dehydration, and severe CNS manifestations tended to occur with greater frequency in the chronic group. When severity of salicylate poisoning was categorized based on a combination of signs and symptoms, mild cases occurred more frequently in the chronic group. Finally, systemic acidosis (pH less than 7.32) was found more frequently in the chronic group (P less than .01), more frequently in patients with severe manifestations than in those with mild manifestations, and in patients with dehydration (P less than .01) and severe CNS manifestations (P less than .05). Based on the variables evaluated, chronic salicylism produces a greater morbidity than does acute salicylate poisoning in the pediatric patient.