The water-soluble crystallins from normal human lenses (n = 32), cataractous lenses of diabetic patients (n = 9) and cataractous lenses of nondiabetic patients (n = 9) were analyzed with fast-performance liquid chromatography. Six different crystallin classes were separated reproducibly by chromatography on Superose 6. The fractions were identified as alpha H, alpha L, beta H, beta L1, beta L2 and low-molecular-weight (LMW) crystallins by their elution order and molecular mass. The results obtained show that during lens aging there is a progressive increase in alpha H-crystallin and a decrease in alpha L-crystallin content, while no significant age-related changes were observed in the LMW fraction. Analysis of changes in crystallin content in human cataractous lenses showed that apparently cataractogenesis can be described as an acceleration of the normal aging process. Important differences were found between the chromatographic profiles of cataracts from diabetic and nondiabetic patients mainly in the LMW fraction, suggesting that in cataract formation of diabetics alternative mechanisms may be superimposed on the normal aging process.