Background and Objectives: Intrathecal fentanyl provides rapid profound analgesia in labouring parturients in the dose range of 10-50 mcg. Therefore, this study was taken up to compare the effects of three different doses of intrathecal fentanyl (15mcg, 20mcg and 25mcg) with regards to onset and duration of analgesia and to find the effective and safe dosage of the drug for labour analgesia. Materials and Methods: A comparative double blinded RCT was performed on 90 term multigravida parturients after obtaining approval from Institutional Ethical Committee. They were divided randomly into three groups (Groups A, B and C) with 30 parturients each. At cervical dilatation of 3-5cm, they received intrathecal fentanyl 15mcg, 20mcg or 25mcg respectively. In all groups, variables such as HR, SBP, DBP and MBP, SpO2, pain assessment by VAS and sedation score by RSS were recorded at different points during the course of labour and mode of delivery and APGAR score was noted after the delivery of the baby. Results: The demographic data was comparable between the groups. The mean duration of onset of analgesia was 13+/-1 min, 9+/-1min and 5+/-1 min in groups A, B and C respectively.