We evaluated change in body mass (BM) and stature (S) in 51,333 National Football League (NFL) players from it's inception in 1920 through 1996. Data came from official 1920-1996 NFL rosters (Sports Encyclopedia, 1982, 1987) and Official NFL League Records and Facts Book, 1988-1996, Workman Publishing). The comparisons focuse on offensive lineman and tight ends (OL: N=13,528) and skill position players (SPP: QB's, receivers, run backs; N=14,216). The data represent all OL and SPP players from each NFL team. Results: BM of SPP increased 10% from 1920 (85.5 kg) to 1996(94,0 kg), while BM for OL increased 53% over the same period (85.5 kg to 130.8 kg). In 1920, OL and SPP weighed the same. From 1980, the rate of increase in BM differed from the rate in 1920-1935, 1935-1965, and 1965- 1980 (P<0.05). S for SPP peaked in 1979 (184.5 cm), but only rose 1.8% from 1920 to 1996. For OL, S increased 8.1% from 1920 (179.2 cm), achieving stability from 1985 to 1996 (193.5 cm). From 1920 to 1996, Body Mass Index (BMI) increased 6.2% for SPP (26.2 to 27.9) and 31.1% for OL (26.6 to 34.9 kg/m2). Conclusions: Over 76 y, BM increased 0.6 kg/y for OL while stabliziing for SPP. The 0.19 cm/y increase in S means that by 2007, OL should attain 195.5 cm (6 ft 8 in) and weigh 136.1 kg (300 lb). Unfortuneatley, a BMI =35.6 kg/m2 would clasify them as high disease risk.