The periodontal ligament injection has been promoted as a primary anesthesia technique. To be useful, however, any anesthetic approach must meet several criteria. First, there must be adequate depth of anesthesia; second, onset of anesthesia should be sufficiently rapid; third, duration must be sufficient to complete the procedure; fourth, discomfort should be minimal during and after the injection; and fifth, the injection must be safe to periodontium and pulp during operative or other procedures. In reviewing the clinical and experimental literature as to the factors described above, the periodontal ligament injection does not meet all of the necessary requirements for a primary technique. It is, however, apparently safe to the periodontium and to the pulp when used in conjunction with certain operative procedures.