Do collagen fibrils of the periodontal ligament shrink with age? Certainly not! Based on the quantitative estimation of over 25000 periodontal ligament collagen fibrils at 3 periodontal levels of 28 freshly extracted human teeth, using 10‐ to 75year‐old subjects and high resolution electron micrographs evaluated planimetrically, the present study demonstrates with data obtained from 2 sampling procedures that the diameter of the average collagen fibril, i.e., 54 to 59 nm, is rather constant throughout the human life span. This is particularly true for the vast majority of comparatively large fibrils (i.e., 57 to 64 nm), while a numerically limited population of small fibrils (i.e., 40 to 48 nm) in fact increased in diameter with age. These results are discussed in view of analogous data for other connective tissues and of the functional and metabolic status of such tiss