Objective; Perfusion index is being regarded as a noninvasive monitoring aid for timely detection of hypotension following subarachnoid block. primary aim was to establish whether trend in Perfusion index(P I) detects hypotension before the changes in noninvasive blood pressure values. Material and method; 104 pregnant women posted for elective caesarian section under Sub arachnoid block were included under the study convenience non-probability sampling. Following co loading with balanced salt solution, all patients received same dose of spinal bupivacaine with monitoring of haemodynamics.