PURPOSE: Strenuous training can be associated with amenorrhea leading to amenorrhea-related accelerated bone loss. Insufficient calorie energy, calcium, and/or protein intakes can also be frequently encountered in women with intense training, possibly contributing to bone loss. Long-distance runners with or without regular menses (age range 19-37 yr) were prospectively studied. METHODS: Changes in areal bone mineral density (BMD) were measured at 1-yr interval. RESULTS: Among 10 eumenorrheic, 11 oligo-amenorrheic, and 9 oral contraceptive users, there was no difference in energy, calcium, or protein intakes. Baseline BMD values were significantly lower in the oligo-amenorrheic group than in the two others at the level of lumbar spine (anteroposterior view: 0.941+/-0.039 in oligo-amenorrheic vs 1.077+/-0.029 or 1.051 +/-0.017 g x cm(-2), P < 0.005, in the eumenorrheic and contraceptive user groups, respectively) but not in weight-bearing bone such as proximal and midshaft femur. Over a 1-yr interval, during which the three groups did not differ in terms of running distances and dietary intakes, oligo-amenorrheic women displayed a significant decrease in lumbar spine BMD in lateral view (-0.049+/-0.012 in oligo-amenorrheic vs -0.001+/-0.013 and 0.014+/-0.012 g x cm(-2), p < 0.005, in the eumenorrheic and contraceptive user groups, respectively). We did not detect any significant change in femoral neck, trochanter, or midshaft BMD. CONCLUSIONS: Oligo-amenorrhea in long-distance runners, with adequate dietary intakes, was associated with a decrease in BMD affecting more the lumbar spine than the proximal and midshaft femur during a 1-yr follow-up.