This chapter contains sections titled: Indications Advantages Disadvantages Contraindications Procedure Preparation and Materials Patient Positioning Median Approach (Midline) Advancing the Introducer Introducing the Spinal Needle, Puncture of the Subarachnoid Space Removing the Stylet Experience Shows that Failure is Usually Due to the Following Causes: Alternative Techniques Paramedian Approach Positioning of the Patient After the Injection Hyperbaric Spinal Anesthesia Isobaric Spinal Anesthesia Hypobaric Technique Fixation Phase Properties of Local Anesthetics in the Subarachnoid Space Local Anesthetics Hyperbaric Technique Isobaric Technique Unilateral Spinal Anesthesia Definition Indications Advantages Disadvantages Contraindications Procedure Injection Technique Dosage Complications Factors Affecting the Spread and Duration of Spinal Anesthesia [66] Spread Duration