OBJECTIVE: Review the theoretical bases on the maintenance of the acid-basic balance, the pathophysiology of the disturbances and its therapeutics in the child.METHODS: References were obtained from computerized searches on the National Library of Medicine (Medline), recent review articles and personal files.RESULTS: Acid-basic disturbances are frequently found in critical ill children. Their pathophysiology and main causes are a complex and multifactorial process. The management depends on precocious diagnosis and of the understanding of the base cause. The treatment should be adjusted for each disturbance and its base cause. Frequently it requests an aggressive correction and continuous monitoring.CONCLUSIONS: The knowledge of the physiology of the acid-basic balance as well as the understanding of the pathophysiology of the main disturbances associated to the clinical situations represent a challenge for the pediatrician. The management of acid-basic balance demands appropriate and careful intervention.