OBJECTIVE To investigate the effects of selective spinal anaesthesia with low-dose bupivacaine alone and in combination with various doses of fentanyl, on blockage, haemodynamics, quality of anaesthesia, perioperative complications, and hospital release criteria. METHODS This prospective study included 45 ASA I-II patients (age range: 20-77 years). The cases were randomised into 3 groups: Group 1 (n = 15) 0.8 ml of 4 mg 0.5% hyperbaric bupivacaine; Group 2 (n = 14) 1.3-ml solution of 4 mg 0.5% hyperbaric bupivacaine + 25 microg of fentanyl; and Group 3 (n = 14) 1.1-ml solution of 3 mg 0.5% hyperbaric bupivacaine + 25 microg of fentanyl. A double-blind design was employed and all patients were injected through L3-4 or L4-5 using a 25G point spinal needle. Sensory-motor blockage starting and ending time, maximum level of sensory-motor blockage, and grade and quality of anaesthesia were recorded. Haemodynamics, and respiration rates, and side effects were evaluated. Times for ability to pass to the stretcher without aid, walking, micturition, release from the hospital, and the first time an analgesic was needed were recorded. RESULTS The time when an analgesic was first required was longer in the groups in which an opioid was added, and the shortest release time from the hospital was observed in Group 3. Other parameters remained similar across all groups. CONCLUSIONS Low-dose bupivacaine, with or without fentanyl, can be used safely in lower extremity surgery and can provide rapid and safe release criteria.