The posterior circumflex humeral artery (PCHA) travels together with the axillary nerve through the quadrilateral space of the shoulder. Angiographic occlusion of this artery upon abduction and external rotation (ABER) of the arm has been accepted as evidence of mechanical compression of the axillary nerve and thus considered pathognomonic of quadrilateral space syndrome (QSS). The specificity of this sign for QSS has however been called into question as there are, to date, limited data on the incidence of axillary neurovascular compression during ABER in a normal population. We set out to determine the rate of stenosis or occlusion of the PCHA on ABER in healthy volunteers using ultrasound.Healthy volunteers asymptomatic for shoulder complaints were recruited from patients attending the clinic for ultrasound imaging not related to the shoulder, as well as volunteers among staff. Doppler sampling of the PCHA of both shoulders of participants was conducted in neutral and abduction and externally rotated positions. Each shoulder was treated as a separate entity.Results showed that 15/93 (16%) of shoulders demonstrated Doppler ultrasound evidence of occlusion or significant stenosis in the absence of shoulder complaints.Occlusion or stenosis of the PCHA on ABER is an uncommon finding in an asymptomatic population. Axillary neurovascular compression is unlikely if colour Doppler ultrasound does not show PCHA compromise during ABER.