Objective: Secondary hypertension is an uncommon form of hypertension and universal screening is not beneficial or cost-effective. Consequently, investigation is reserved for selected cases, according to clinical suspicion, and is often referred to a specialist. The aim of this study was to characterize the evaluation of secondary hypertension in the Internal Medicine Outpatient Department of a portuguese hospital. Design and method: This longitudinal retrospective study analysed patients referred to our Internal Medicine Outpatient Department for hypertension evaluation in 2021. Patient records and results were analysed, focusing on indication for evaluation, testing performed and identified causes of secondary hypertension. Results: A total of 147 patients were referred for hypertension evaluation, 7 (4,76%) of which were explicitly referred for secondary hypertension screening. Testing was conducted in 105 patients (71,43%), with basic evaluation (CBC, renal function, thyroid function) in 71 patients (48,30%) and additional testing (such as endocrine, renovascular, obstructive sleep apnoea screening) performed in 34 patients (23,13%). Considering age criteria, resistant hypertension, and other clinical clues, 60 patients (40,82%) had a documented indication for additional testing for secondary hypertension. Additional testing was requested in 5 patients (3,40%) not meeting these criteria, most of whom needed testing to follow-up investigations ordered in primary care without clear indication. Conversely, a small proportion (6,12%) met criteria for additional testing that wasn’t requested: 22% already had a previous screening ordered in primary care negative for secondary hypertension; 44% were evaluated for hypertension-mediated organ damage without further screening. Patients in which specific evaluation was complete at the time of this study, a secondary cause was identified in 9 patients (6.12%), all with a previous diagnosis of Obstructive Sleep Apnea. Conclusions: The prevalence of secondary forms identified didn’t significantly differ from the described 5-10% overall prevalence of secondary hypertension and reiterated the identification of OSA as an exceedingly common recognized cause of hypertension. This study emphasised that extensive testing was mostly non-diagnostic and was associated with inconclusive results leading to further investigations, raising costs and risks. This suggests that careful selection of patients and method of screening by a specialist is beneficial.