Background: In 2007, the Hospital Infantil Los Ángeles (HILA) in Colombia implemented a slightly-modified version of the WHO guidelines for the diagnosis and management of malnutrition during childhood. Objective: To evaluate the efficacy of the WHO-HILA protocol in children hospitalized with severe, chronic marasmus and kwashiorkor malnutrition (MS-KWK) in 2007 and 2008. Material and methods: In this descriptive retrospective study the records of 100 children hospitalized with MSKWK were initially evaluated. Of these, 30 fulfilled the inclusion criteria: children of both sexes with a primary diagnosis of MS-KWK. Patients with any chronic disease liable to cause malnutrition were excluded. Anthropometric parameters, clinical signs and biochemical indicators of malnutrition were assessed upon admission and again at discharge following application of the WHO guidelines. Univariate analysis was performed for each study variable; serum hemoglobin and albumin levels on admission and at discharge were compared, and data were subjected to bivariate analysis. Results: Marasmus was diagnosed in 23.3% of children, kwashiorkor in 73.3% and marasmic kwashiorkor in 3.3%. The major clinical findings were: edema (70%), emaciation (40%), "flag sign" hair (42.86%), low serum albumin (93%) and anemia (80%). Thirteen children following the WHO-HILA protocol showed a significant nutritional status improvement (p < 0.05), whereas no improvement was noted in the 17 children not treated according to the protocol. Conclusions: Application of the WHO-HILA protocol was associated with reduced morbimortality in children with marasmus-kwashiorkor malnutrition. Implementation of this protocol should therefore be considered in all children´s hospitals in countries where this disease is prevalent.