Objective: Topical treatment options in chronic rhinosinusitis (CRS) are growing with our increased understanding of the inflammatory process. Additives to irrigation devices have become popular. Additives such as menthol provide little more than sensory feedback. However, glucocorticosteroids and antibiotics represent powerful pharmaceutical agents for which we have little knowledge regarding patient exposure and absorption. There is little data on fluid retained after nasal irrigation. The purpose of this study was to determine the residual volume and percentage of total nasal irrigation that is retained from a neti pot (NasaFlo) or squeeze bottle (Sinus Rinse). Study Design: Cross-sectional study. Setting: Tertiary rhinologic clinic. Methods: Patients with CRS were already using saline irrigation in their treatment. Participants were divided into pre and post sinus surgery (ESS). Control irrigations on 17 healthy patients with no sinonasal complaints were collected. Nasal irrigation was performed with accurate collection of the excess to determine retained amount. Results: Overall retention of fluid was 2.5 ± 1.6 percent. This represents only 5.8 ± 3.8 mL for the 240-mL irrigations. Squeeze bottle and neti pot were similar: 2.3 ± 1.3 percent and 3.0 ± 2.2 percent, respectively (P = 0.23). CRS (pre-ESS) patients had the least retained volume: 1.4 ± 1.2 percent. Post-ESS retained volume was 2.36 ± 1.18 percent. Control patients retained 2.2 ± 1.2 percent. Conclusions: Quantification of the residual volume has important implications for the treatment of inflammatory disease with saline, as well as for potentially novel topical therapies. The information helps to define the fluid dynamics during nasal irrigation. The data are important to address concerns regarding drug or salt exposure from a very common intervention.