The levels of advanced nonenzymatic glycation endproducts (ACE) were investigated by spectrofluorimetry in eye lens proteins obtained from rats with experimental diabetes of 3 and 6 months duration and from normal age-matched control rats. Diabetic animals showed higher AGE levels at both times studied. However the older control animals showed protein ACE levels comparable to those of the experimental 3 months diabetic group. These data suggest that a pathological phenomenon such as enhanced nonenzymatic glycation, associated to diabetic hyperglycemia, can be considered as a process leading to an accelerated aging of proteins. Thus experimental diabetes mellitus may be used as a model to investigate physiological protein senescence.