The aim of this study was to demonstrate metabolic changes in the small joints of the hand due to rheumatoid arthritis by means of 31-phosphorus spectroscopy. Suitable measurements were developed and 11 normals and 12 patients were then examined during the course of treatment. Relative concentration of low energy phosphorus metabolites was increased in arthritic joints. The phospholipid quotient (phosphomonoester/phosphodiester) and the relationship of inorganic phosphate and beta-nucleoside triphosphate were significant factors during the course of individual treatments.