BACKGROUND: To date, information about the frequency of electrolyte disturbances among children with severe falciparum malaria is limited. METHODS: We describe changes in potassium, calcium, magnesium, and phosphate levels in 56 Kenyan children (42 who survived and 14 who died) admitted to the hospital with clinical features of severe malaria (impaired consciousness or deep breathing) complicated by acidosis (base deficit, >8 mmol/L). RESULTS: Mild-to-moderate hypercalcemia was common at admission, particularly among children with severe anemia. Severe hyperkalemia complicated falciparum malaria in 9 children (16%), of whom 7 (78%) died, generally soon after admission. Hypokalemia, hypomagnesemia, and hypophosphatemia were uncommon (<7% of children) at admission but developed in >30% of children within 24 h. Hypocalcemia was infrequent (<5% of children) at any time point. Apart from administration of potassium, electrolyte deficiencies were not corrected and were not associated with an adverse outcome. CONCLUSIONS: At admission to the hospital, hyperkalemia may complicate cases of acidosis due to severe malaria and is associated with high, early mortality. After admission, mild asymptomatic deficiencies in magnesium and phosphate levels were common but were not associated with any deleterious effect. Thus, routine correction when serial measurement of electrolyte levels cannot be performed is unwarranted. Asymptomatic potassium deficiency developed despite provision of this electrolyte at maintenance doses. Further studies are justified but are unlikely to be a major research priority because, as these data suggest, the impact on mortality would at most be limited.