Although hyperostosis frontalis interna (HFI) has been documented in the medical literature for over 300 years, its etiology remains undetermined. It is generally assumed to be associated with hormonal disturbances of the gonads. The aim of this study was to examine the association between androgen deprivation and development of HFI in males. Two groups of males over 60-years old were compared: a control group that included 180 healthy males, 45 suffering from benign prostatic hypertrophy (BPH) and a study group of 127 males with prostate cancer: 67 who received complete androgen block treatment, and 60 who received different treatments or none at all. CT head scans were used to identify and classify HFI (Brilliance 64, Philips Medical Systems, slice thickness 3 mm × 1.5 mm). It was found that males who received a complete androgen block manifested significantly higher prevalence of HFI compared to healthy males. However, no significant difference in HFI prevalence was found between males suffering from BPH and healthy males or males with prostate cancer who had not received a complete androgen block. A positive association between length of hormonal treatment and manifestation of HFI was shown. It can be concluded that BPH does not promote development of HFI; males who are hormonally treated for prostate cancer are at a higher risk of developing HFI compared to healthy males; the longer the duration of hormonal treatment, the higher the risk of developing HFI. Anat Rec 293:1333–1336, 2010. © 2010 Wiley-Liss, Inc.