Study objectives The aim of our study was to establish the angle of needle insertion from the anterior chest wall during ultrasound-guided infraclavicular brachial plexus block and to examine for any correlation between body mass index (BMI) and insertion angle. Design This is a prospective observational study. Setting The setting is at an operating room, university-affiliated teaching hospital. Patients The patients are 23 American Society of Anesthesiologists physical status 1-3 patients scheduled to undergo elbow, forearm, or hand surgery under regional anesthesia with or without general anesthesia. Interventions The intervention is infraclavicular brachial plexus block with or without perineural catheter insertion. Measurements The measurement is the angle of needle insertion in relation to the anterior chest wall, BMI, and needle visibility as graded by the anesthesiologist. Main results Twenty-three patients were studied. The mean (SD) BMI was 28.5 (5.4). The median (range) of angle of needle insertion was 50 (33-60). The Pearson correlation coefficient for BMI and angle of needle insertion was 0.357. There were no reported complications. Conclusions The median (range) angle of needle insertion in relation to chest for our study patients was 50° (33°-60°). The needle visibility was rated difficult, requiring hydrolocation or "heeling-in," in 39% of cases. There was a moderate correlation between BMI and angle of insertion. Despite difficulties with needle visualization, the ultrasound-guided infraclavicular brachial plexus block provided reliable analgesia.