The leading cause of patient death from hospital-acquired infections is pneumonia. Ventilator-associated pneumonia (VAP) is a common, significant, life threatening infectious disease that occurs in subjects who are intubated with an endotracheal tube and require mechanical ventilation. The primary objective of this study is to evaluate the safety and effectiveness of using photodynamic treatment (PDT) to significantly reduce microbial biofilm (by at least 2 logarithms base 10) that commonly grow inside an endotracheal tube of intubated subjects. Secondary objectives include the following: comparison between PDT treated subjects and those receiving standard-of-care medical treatment (control group) will be made regarding the proportion of subjects who develop tracheobronchitis or VAP during the study period, as documented by fever, new radiographic density, purulent tracheal aspirates, and leukocytosis or leukopenia; comparison of pathogen sensitivities between the treatment and control groups (pathogen sensitivities will be performed on both the endotracheal tube and sputum cultures); comparison of the time to extubation between the treatment and control groups; and comparison of the length of hospitalization between the treatment and control groups. Subjects who will be or who have been recently (within 24 hours) intubated orally with an endotracheal tube and placed on a mechanical respirator are eligible to participate in the study. Subjects will be randomized into either a treatment group or a control group. In the treatment group, the lumen of the subject's endotracheal tube will receive PDT once every 8 hours (3 times per day). The control group will receive no PDT of their endotracheal tube. Treatment group subjects will have a culture sample taken of their endotracheal tube before and after PDT (once per day during the 1st PDT treatment of the day) to determine the effectiveness of PDT to reduce microorganisms. Control group subjects will have their endotracheal tubes cultured for microorganisms once per day at the same time as the treatment group. A sputum culture will be taken from both study groups once per day at the same time of the day. Photodynamic treatment effectiveness will be determined by comparing the quantitative cultures taken before and after PDT within the treatment group as well as comparing the cultures between the treatment and control group. A total of 90 subjects (45 treatment and 45 control) will be studied at each of 3 sites for a grand total of 270 subjects (135 treatment and 135 control). The primary objective will be measured by quantitatively counting the microorganisms present in the endotracheal tube before PDT and after PDT and comparing differences. Quantitative counting will be done using standard microbiologic methodology at each site. Outcomes will also be measured to evaluate the following secondary objectives: quantitative microbiological cultures will be taken from the subject's endotracheal tube in both the control group and treatment group for comparison; a statistical comparison of the incidence of tracheobronchitis and/or VAP will be recorded for both the treatment and the control groups; pathogen sensitivities will be performed and recorded for both the treatment and the control groups including comparisons between both the sputum and endotracheal tube cultures; a statistical comparison of the time from intubation to extubation will be made between the treatment and control groups; and a statistical comparison of the recorded length of hospitalization will be made for both the treatment and the control groups.