The role of physical therapists in critical care has been evolving. Of interest to this section, traditional PT care in the ICU focused on interventions for respiratory conditions, using techniques such as percussion, manual hyperinflation, suctioning, and bed exercises. As our knowledge of the importance of early mobilization has evolved, as evidenced by changes in how quickly patients are out of bed following cardiac surgery, the interventions in physical therapy have changed. The physiologic rationale for early mobilization has been discussed since the early 1990s in papers written in part by leaders in cardiovascular and pulmonary physical therapy.1 What has been lacking is strong evidence of the benefits of early mobilization in critically ill patients. In the past few years, the number of poster and platform sessions at the Combined Sections Meetings focused on physical therapy in critically ill patients has increased. Similarly, the number of published articles on this topic is growing. The topic for this special issue developed in response to these trends. Our call for papers resulted in a variety of manuscripts. We have a systematic review of mobilization in the ICU, which focuses on both safety and effectiveness outcomes. There is good evidence to support the effectiveness of early mobilization, even in patients on mechanical ventilation. Several interesting case examples are included that will be very useful in helping clinicians determine the types of interventions and outcomes most relevant to treating patients in ICU environments. One paper also addresses what can be done in the academic environment to prepare students for work in these complex practice environments. And, we benefit from the expertise of our colleagues in other countries; in this edition, we have examples from Turkey and Australia as well as the United States. The articles chosen for this issue illustrate several treatment trends that will help advance the work of PT in the critical care environment. One of our articles discusses the barriers to treatment of patients in the ICU. This shows us that some barriers, such as timing of medication administration, could be easily addressed, but will require the physical therapist to be committed to active mobilization of patients and demonstrate ability to communicate effectively with other members of the ICU team. Overall, there are relatively few adverse effects of early mobilization, particularly when therapists are observing the physiologic response of patients by monitoring vital signs during treatment sessions. A number of articles discussed in the systematic review provide guidelines for discontinuing treatment based on vital sign responses. This reminds us that we need increasing focus on one of the key tenets of cardiopulmonary physical therapy practice; that we are treating the patient's physiologic deficits in conjunction with movement and functional abnormalities. There is much work to be done in advancing the practice of PT in these critical care environments. What an exciting time of practice to be able to shape the interventions and influence better health outcomes for our patients!