This article provides a reasessment of the nitrate industry in Perú and Bolivia up to the War of the Pacific based on the material provided by the archives of Antony Gibbs and Sons and various contemporary publications. Special attention is given to the succesive changes in the technology of nitrate extraction prior to the introduction of the Shanks system. These improvements were more effective than was previously supposed. Production costs are also analized, output figures are provided for specific "oficinas", and contemporary information is provided on the Peruvian attempts to form a nitrate monopoly.