With this research, we verified the influence of needle caliber on the incidence of headaches in patients after subrachonoid puncture. The sample consisted at 40 patients, divided into two groups of 20 patients. One group was tested with an 80x7 needle during subrachonoid puncture while the other group was tested with an 80x5 needle during the procedure. After the surgery each group was redivided into subgroups of 10 patients; this one subgroup from each larger group was instructed to lie flaton their backs for 24 hours after surgery. The other subgroup from each category was instructed to lie down for just 4 hours after surgery and to then get up and walk around. The results demonstrate a total absence of headaches after surgery in patients who were treated with an 80x5 needle. Of patientes treated with an 80x7 needle, 30% of the subgroup which got up after only 4 to 6 hours experienced headaches, while just 10% of the subgroup which termained laying down for 24 hours expeienced headaches