The authors evaluated the metabolic kinetics of organophosphate compounds in the course of the evolution of galactose cataracts in rat lenses using phosphorous-31 nuclear magnetic resonance (31P-NMR) spectroscopy. Three-week-old rats (Lewis) were fed with a 25% galactose diet for three days, and one, two, three and four weeks. Metabolic changes in the lenses were measured and the following results were obtained: (1) Changes in glycerophosphorylcholine (GPC) levels over the time course were analogous to changes for choline phosphate (CP); both GPC and CP level showed a significant decrease in the galactose-fed sample compared with the controls from three days after ingestion, and then continued to decrease gradually. This suggested that the decrease of GPC was associated with the level of CP. (2) Inorganic orthophosphate (Pi) increased gradually after the ingestion of galactose, reaching a maximum at third week, and subsequently falling. Adenosine triphosphate (ATP) levels did not show any significant changes at one week, but had fallen significantly at two weeks. There might be metabolic pathways for production of ATP without requirement of Pi in the lens for at least the first one week. (3) Adenosine diphosphate (ADP) levels did not show any significant changes at three days, but had fallen significantly at one week. Nucleotide sugar (NS) increased gradually after the ingestion of galactose, reaching a maximum at second week, and then decreasing. This suggested that the ADP was converted to ADP sugar.