The spread of sensory blockade during spinal analgesia using bupivacaine is influenced by a number of factors concerning baricity, positioning, dosage, technique of injection and patient characteristics. The glucose-free 0.5%-solution acts as a hypobaric solution. The interaction of baricity and posture during and immediately after the injection of this solution is of utmost importance. However, the level of analgesia when using hyperbaric solutions seems not to be affected by posture. The dose of bupivacaine is also of great importance, independent of the type of solution used. Of modest importance is patient age, irrespective of baricity, while obesity and injection level only matter when the glucose-free solution is used. Injection speed seems of modest importance, while barbotage and direction of the needle have no or minimal clinical importance. The problem of unpredictability of the sensory blockade, a major one in spinal analgesia, is yet to be solved.