A vaccine, GIV, was prepared by cobalt-60 irradiation of lyophilized M. tuberculosis H37Rv and tested for immunogenic activity in mice. The GIV gave significant protection to mice against challenge doses sufficient to kill all control animals in less than thirty days. The use of an adjuvant significantly increased the immunogenic activity of GIV. Four doses of 0.1 mg or a single 1.6-mg dose with adjuvant gave protection equivalent to that resulting from vaccination with living BCG.