Thirty-four severely injured eyes were operated with pars plana vitrectomy. The nine cases with involvement exclusively of the anterior segment alone were operated with success in all cases. However, the injuries of the posterior segment still reflect significant problems in that only 50 percent obtained successful visual results. This reflects, in great part, the degree of severity of the initial damage. The theoretical rationale for pars plana vitrectomy in penetrating ocular trauma is discussed. Because of the many variables from patient to patient and injury to injury, conflicting clinical impressions as to appropriate management prevail. In the abscence of a definitive clinical trial or suitable experimental model, our guidelines for the role and proper timing of pars plana vitrectomy for penetrating ocular trauma are presented.