Context: Elderly patients exhibit the alterations in their physiological system. This affects the action of anesthetic agent in terms of spread, onset of action on motor block. Aims: Evaluating the efficacy of intrathecal Fentanyl as an adjuvant to intrathecal Bupivacaine (Hyperbaric) in patients undergoing transurethral resection of prostate. Settings and Design: Hospital based cross sectional study was conducted at SVS Hospital and Medical College, Mahabubnagar. Methods and Material: This study was conducted from November 2014 to November 2015. Informed consent was taken. 100 eligible patients as per inclusion and exclusion criteria were randomly grouped into 2 groups with 50 patients each. Group I received 1.5 ml of 0.5% hyperbaric Bupivacaine (7.5 mg). Group II received 1 ml of 0.5% hyperbaric Bupivacaine + 25 g Fentanyl. Parameters like Onset of motor block, Onset of sensory block, Time for two segment regressions, and Total duration of analgesia were studied. Statistical Analysis: The data was analyzed using statistical methods like Chi square Test, Repeated measure ANOVA, Independent samples T test. Results: Addition of Fentanyl 25 ìg to Bupivacaine resulted in significant faster onset of sensory block and motor block. The time taken to reach T10 dermatome level was also faster in group II. Time for two segment regression was faster in group II and was significant. Duration of analgesia was significantly prolonged in group II. Patients were aerodynamically more stable in group II. Conclusion: Intrathecal Fentanyl 25 g with 5 mg of hyperbaric Bupivacaine provides adequate and satisfactory anesthesia for TURP.