This study was designed to investigate whether flaxseed oil (FO) exerts hypocholesterolemic effects similar to ground whole flaxseed (WF) and to gain insight into its hypocholesterolemic mechanism. Forty-eight 6-month-old female Golden Syrian hamsters were either sham-operated (Sham) or ovariectomized (Ovx) and randomly assigned to one of four treatment groups (n = 12/group) for 90 days: Sham, Ovx, Ovx+WF, or Ovx+FO. Hamsters in the Sham and Ovx groups were fed a semipurified diet (control), whereas Ovx+WF and Ovx+FO received the same basic diet supplemented with either WF (15% wt/wt) or FO (amount equivalent to the oil contribution of WF). Ovariectomy significantly (P < .05) increased serum total concentrations by approximately 15%. WF, but not FO, prevented (P < .05) the ovariectomy-induced increase in serum total cholesterol concentration (12% and 4% reduction by WF and FO, respectively). Hamsters fed FO or WF had high-density lipoprotein (HDL)-cholesterol concentrations similar to those of the Ovx hamsters receiving the control diet. Non-HDL-cholesterol concentrations were lowest in the WF group, albeit not statistically different from the other treatment groups. There were no significant differences among groups in serum triglyceride concentration and liver lipids. Both WF and FO more than doubled the hepatic protein levels of 7α-hydroxylase in comparison to the Ovx hamsters receiving the control diet (P < .05). Our findings suggest that increased bile acid synthesis is one of the major cholesterol-lowering mechanisms of flaxseed and that other flaxseed components, aside from its oil, contribute to its hypocholesterolemic property. The cholesterol-lowering effects of other components of flaxseed and their mechanisms of action need to be further explored.