It is felt that WHO criteria for treatment failure are too stringent. Improvement is defined as the return of respiratory rate to below the cut off for that particular age at 48 hours. Some of the children with viral pneumonia will continue to have respiratory rate above the cut off on the first follow-up. These children are otherwise well and show no signs of deterioration of the disease but according to WHO criteria they would be classified as treatment failure. The treatment failure rates hence are influenced by the definitions used.