Methods: Cases were identified by searching de-identified electronic patient records from UK primary-care veterinary practices participating in the VetCompass Programme.Results: The estimated prevalence for hyperadrenocorticism diagnosis in dogs was 0.28% (95% confidence interval 0.25-0.31). Multivariable logistic regression analysis revealed four associated risk factors: breed, breed-relative bodyweight, age and insurance status. The Bichon Frise had 6.5 times the odds (95% CI 3.5-12.1, P < 0.001) of hyperadrenocorticism compared with crossbreds. Dogs weighing more than or equal to their breed mean had 1.7 times odds (95% CI 1.3-2.3, P < 0.001) of hyperadrenocorticism compared with dogs weighing less than the breed mean. Dogs aged 12.0 years and above showed 5.7 times the odds (95% CI 3.7-8.7, P < 0.001) of hyperadrenocorticism compared with dogs aged 6.0-8.9 years. Insured dogs had 4.0 times the odds (95% CI 2.8-5.6, P < 0.001) of hyperadrenocorticism compared with noninsured dogs.Clinical significance: This is the first epidemiological report of a non-referral hospital population of dogs diagnosed with hyperadrenocorticism in the UK and describes important breed, age and bodyweight associations with this disorder which may improve diagnosis and enhance understanding of the underlying pathophysiology.