Objective To study the spontaneous occurrence of hypophyseal cyst in beagle dogs and establish the backgroud information of experimental animals for good laboratory practice ( GLP) ． Methods Sixty beagle dogs ( male∶female = 1∶ 1) aged 8-10 months were used in this study． The incidence of hypophyseal cyst was recorded and analyzed，and their histopathological features were examined by histopathology． Results Almost all the cysts were seen in the pars distalis hypophysis，and the wall was covered by a squamous or cuboidal epithelium． The total incidence rate of hypophyseal cyst was 23. 3% ． The incidence rate in females was 13. 3% and in males was 33. 3% ． Conclusions It is suggested that spontaneous occurrence of hypophyseal cyst in Beagle dogs should be monitored so as to provide correct histopathological backgroud information of the dogs for drug safety evaluation．