The relationship between plasma levels of homocysteine (Hcy) and femur bone mineral density (BMD) was studied in Wistar rats. After 8 weeks of treatment with 0.5 and 1.0 g kg(-1) day(-1) L-methionine the mean plasma levels of Hey were 7.67+/-1.25 and 61.2+/-11.4 mu mol/l, respectively. Only rats treated with the higher dose had Hey levels significantly higher than those of controls, 6.38+/-0.90 mu mol/l (p<0.001). Dual Energy X-ray Absotptiometry was used to measure the BMD, which was significantly lower only in the animals with the highest plasma levels of Hey (p<0.001). This led us to conclude that increased levels of Hcy are associated with risk of decreased BMD.