Background.Spinal anaesthesia, which is one of the techniques for infraumbilical surgeries, is most commonly criticized for limited duration of postoperative analgesia.Aim of the Work.The aim of this study was to decrease bupivacaine dose used in spinal anesthesia in patients undergoing orthopedic lower limb surgery and reduce its possible side effects.Patient and Methods.Sixty adult patients of both sexes, divided into three.Group Creceived 2.5 mL bupivacaine and 0.5 mL saline 0.9%.Group Areceived 2.5 mL bupivacaine and 0.5 mL midazolam.Group Breceived 2.5 mL bupivacaine and 0.5 mL magnesium sulphate.Results.As regards onset of both motor and sensory blockade, there are a significant decrease in group A and a significant increase in group B as compared to group C, with a significant decrease in duration of motor blockade and significant increase in duration of sensory blockade in both group A and group B, respectively, as compared to group C, with a significant decrease in the duration of sensory blockade in group B as compared to group C.Conclusions.These results suggested that intrathecal midazolam as an adjuvant for bupivacaine increases the duration of both sensory and motor blockade more than that of magnesium sulphate.