Aromatase inhibitors improve relapse-free survival in early breast cancer, but there is concern about possible detrimental effects on bone mineral density (BMD) and plasma lipids. This paper presents the results of a 2-year study evaluating the effects of exemestane versus placebo on BMD, bone markers, plasma lipids and coagulation factors, including a 1-year follow-up after termination of treatment in 147 patients. During treatment, the mean annual rate of loss of BMD in the lumbar spine was 2.17% in the exemestane group versus 1.84% in the placebo group (n.s.) and 2.72% versus 1.48%, respectively, in the femoral neck (P=0.024). A loss of BMD above that expected in both arms of this study could be due to low vitamin D status (88% of all patients had vitamin D levels <30 ng/ml). The changes observed with exemestane were partially reversed during a 1-year follow-up, with no significant difference between the two arms. Similarly, the moderate decrease in high-density lipoprotein (HDL)-cholesterol was reversed. The bone marker values decreased, although a difference at 6 months of follow-up was still recorded, in particular for the markers of bone synthesis.