To estimate the prevalence of orthostatic hypotension (OH) in patients 80 years old and over attending a primary care unit. To relate OH to the most prevalent pathologies and to the most used drugs. Transversal observational study. Primary care unit, Santiago de Compostela. Eighty one patients 80 years old or over representative of a primary care unit were recruited. Ten patients were excluded. Blood pressure was measured in decubitus and later in erect position first immediately after standing and then after 3 minutes. Diagnoses and active treatments were reviewed in the electronic clinical history and through an interview with the patient and caregiver. In 26.76% of patients the systolic blood pressure fell by 20mmHg or more and/or the diastolic blood pressure fell by 10mmHg in the instant following the postural shift. In 16.90% of patients the drop persisted after 3 minutes of standing from decubitus position. None of the patients was diagnosed with OH. The highest prevalence ratio was observed for diabetes mellitus (1.6; P=.412), not existing differences for arterial hypertension (P=.881). OH related in a statistically meaningful way to the use of renin angiotensin aldosterone system inhibitors (OR: 8.174, CI95%: 1.182-56.536); P=.033] and benzodiazepines (OR: 5.938, CI95%: 1.242-28.397; P=.026)]. OH had a prevalence of 16.90% among the elderly patients who had a consultation. Its connection with some drugs (renin angiotensin aldosterone system inhibitors and benzodiazepines) must be considered. Copyright © 2018 The Authors. Publicado por Elsevier España, S.L.U. All rights reserved.