Having demonstrated clinical efficacy in cardiology, urology, and ophthalmology, balloon catheters were adapted for the paranasal sinuses in the early 2000s, highlighted by US Food and Drug Administration (FDA) approval of the first Acclarent balloon catheter device in 2005 (Acclarent Inc). In the ensuing years, multiple devices have been developed and refined for rhinologic indications, and balloon dilation of the paranasal sinuses has been the subject of often passionate discourse over its role as a treatment option for patients with chronic rhinosinusitis (CRS). In contradistinction to traditional models of sinus surgery based on excision of inflamed, obstructive tissue, the balloon dilation model of surgical treatment is based on tissue displacement and ostial dilation. The safety of balloon dilation technology has been well established through large registries and cumulative patient experience. Although complications have been described, there does not appear to be disproportionate risk to the patient from balloon dilation relative to other surgical technologies for sinus surgery. Efficacy has been more difficult to assess. As gauged by technical success of cannulating the sinus ostium and completion of the balloon dilation, the technique is largely successful, with 80% to 97% rates of procedure completion in most series. Newer fiberoptic lightguided devices have enabled more ergonomically favorable instrumentation while avoiding the exposure to radiation from fluoroscopy, formerly required of the procedure. However, assessments of clinical outcomes of balloon dilation are undermined by inadequacies of study design in many cases. For example, when multiple sinuses are treated by balloon dilation or when hybrid FESS is performed (combination of balloon dilation plus standard FESS), and only a global assessment of improvement is made, it is difficult to discern the potential clinical effect of balloon dilation on a single diseased sinus. In assessing the clinical efficacy data available to date, we should be open to potentially novel understandings of sinus physiologic characteristics in assessing clinical responses to selective dilation. For example, Stankiewicz et al identified improvements in anterior ethmoid sinus opacification when dilating the maxillary sinus ostium through a transantral approach. While the balloon may have dilated the ethmoid infundibulum, it likely left intact the anatomic structure of the drainage pathway of the bulla ethmoidalis, which drains medially away from the ethmoid infundibulum. This finding is surprising and challenges our traditional thinking about what is necessary to effect resolution of inflammatory changes in the paranasal sinuses. At the same time, while we must be open to reexamining our preconceptions about the anatomic contributions to the pathophysiologic characteristics of CRS, we must also be critical in evaluating the outcomes reported in the literature. Our current understanding of CRS pathophysiologic characteristics suggests a much more complex and nuanced heterogeneity of disease subtypes rather than a simple “plumbing” problem that can be broadly applied to all varieties of CRS. Thus we must be careful to review the inclusion and exclusion criteria for any given trial to understand how its results might be applicable to our own patients. We must also recognize potential sources of bias and confounding in the study design and interpret the data accordingly. Currently, the overall quality of evidence to support the efficacy of balloon dilation is decidedly mixed. Large case series have been reported, but various trials have been undermined by one or more of a variety of potential weaknesses: lack of Author Affiliation: Division of Rhinology and Endoscopic Skull Base Surgery, Department of Otolaryngology–Head and Neck Surgery, Stanford University School of Medicine, Stanford, California. Peter H. Hwang, MD