Bupivacaine is one of the most commonly used local anaesthetics for spinal anaesthesia. Its clinical properties may vary depend ing on the baricity of the solution, which affects drug spread within the cerebrospinal fluid and the characteristics of the block. The aim of this narrative review was to compare hyperbaric and isobaric bupivacaine used for spinal anaesthesia in adult pa tients (>18 years), based on randomised clinical trials. A literature review of randomised clinical trials comparing hyperbaric and isobaric bupivacaine in adult patients was conducted. The analysis addressed sensory and motor block characteristics, haemodynamic parameters, duration of anaesthesia, and recovery time after surgery. In most studies, hyperbaric bupivacaine was associated with a faster onset of sensory and motor block, as well as more predict able spread of anaesthesia. Isobaric bupivacaine was more frequently associated with a longer block duration and prolonged postoperative analgesia. The effect of baricity on haemodynamic stability was variable; however, vasopressor requirements were comparable between groups in most studies. The baricity of bupivacaine appears to influence the clinical profile of spinal anaesthesia. Both hyperbaric and isobaric bupiv acaine can be used safely, and the choice of formulation should be individually adjusted by the physician to the clinical circum stances and the needs of each patient.