Evaluate the frequency of positive aspirations and complications resulting from anesthesia of the inferior alveolar nerve by the direct technique. The sample was composed of 138 anesthetic injections applied with Duflex syringes with reflux. The anesthesia was applied in patients of both sexes of various ages for procedures in which such anesthesia would be necessary. The results showed 4.3% of positive aspirations in vivo. When the percentages of positive aspiration on the right and left sides were compared, no significant association was found. A greater number of positive aspirations was observed in the 15-30-year-old age group. It is emphasized that the only type of complication associated with positive aspirations was hematoma. The percentage of positive aspirations from inferior alveolar nerve block by the direct technique is significant, and for the most part they do not appear in the form of a thin thread, requiring great care on the part of the person applying the anesthesia.