Osteopenia/osteoporosis (O/O) has been associated with allogeneic stem cell transplantation (alloSCT). We retrospectively reviewed 102 patients undergoing a first alloSCT from 2000 to 2005 at our center to evaluate the prevalence of O/O⩽ 6 and> 6 months post-alloSCT. Fifty-six patients did not have a dual energy X-ray absorptiometry (DXA) scan following alloSCT. Approximately half (n= 13/27) of those with a first DXA scan⩽ 6 months post-alloSCT had O/O and a similar rate (n= 9/19) was seen in those with a first DXA scan> 6 months. There were no significant differences in patient characteristics between the normal and O/O groups. The dual femur (DF) appeared to be more vulnerable to alloSCT-induced bone mineral density (BMD) loss than the lumbar spine (LS), regardless of screening time. O/O patients were treated with bisphosphonates and 41% had a repeat DXA scan post-treatment. No patient developed jaw osteonecrosis and significant BMD improvement was seen at the LS (mean BMD, 1.03±0.13 vs 1.08±0.12, P= 0.004) but not the DF (mean BMD, 0.84±0.06 vs 0.85±0.08, P= 0.29), indicating BMD loss at the DF is more resistant than the LS to antiresorptive therapy. Our results demonstrate that O/O is an early and late complication post-alloSCT and bisphosphonate treatment reverses BMD loss at the LS.