An endometrial thickness greater than 5 mm warrants follow­up. One study showed that most women receiving tamoxifen  did not have symptoms such as bleeding. Nonetheless, almost  half   of   the  women  had  abnormal  endometrial thickness on  ultrasound.  Less  than  1%  of   women  receiving  tamoxifen  therapy develop endometrial cancer even though the risk may  be  increased  sixfold.  Most  women  receiving  tamoxifen  have  been doing so  for more than  5 years, and most present  with  postmenopausal bleeding. There is a considerable reduction in  endometrial thickness at 6 months after cessation of  therapy.  Sonohysterography  is  an  excellent  modality  to  delineate  the  endometrial  contents  better.  Sonohysterography  is  the  most  likely imaging procedure to reveal polyps, which are the most  frequent  abnormality  in  women  receiving  tamoxifen  treat­ment. Tamoxifen-related polyps tend to be larger and have an  increased rate of malignant changes compared with endome­trial  polyps  in  the  general  population.  A  hyperechoic  endo­metrium  with  small  cystic  spaces  is  the  classic  nding  with  tamoxifen therapy (see Figure). Many of these cystic spaces  represent  endometrial  polyps;  however,  cystic  hyperplasia  may  also  have  this  appearance.  Two-dimensional  or  three-  dimensional  sonohysterography  is  often  helpful  to  elucidate  the cause of  endometrial stripe thickening.