Hi Joeby, this happened to me after I was switched from Tamoxifen to Arimidex some months ago. I only had a day or so of bleeding but my oncologist put me straight back on Tamoxifen as although, like you, my hormone levels were showing I was post-menopausal they can sometimes fluctuate a bit. She also sent me for a pelvic ultrasound (internal & external) to check the lining of the uterus etc. That was all ok. I also had to see my gynaecologist to be checked over - again all ok. I'm due for revision with my oncologist in Feb & expect that she will try me on Arimidex again then as my hormone levels appear to be "rock bottom" :-) Apparently this does happen quite often but you do need to make sure you are on Tamoxifen if there's any chance you are still pre-menopausal. Hope this helps, Jane xx