Objective: The study aimed to determine the role of low frequency ultrasound in patients with Chronic Rhinosinusitis with Nasal Polyposis (CRS-NP) and recovery after Endoscopic Sinus Surgery (ESS) using Sino Nasal Outcome Test 22 (SNOT-22) questionnaires, modified Lund MacKay endoscopic appearance, and histopathologic examination. Methods: Study design: Single Blinded Randomized Controlled Trial Setting: Tertiary government hospital Subjects: 42 adult Filipinos aged 19 to 76 years-old diagnosed with Chronic Rhinosinusitis with grade 2 and 3 Nasal Polyposis and failure of maximal medical management (3-month course of antibiotics, nasal douche, topical steroids and other modalities) between June 2013 to June 2015 were randomized into two groups of 21 participants each-- the ultrasound-treated group and control group. Specimens (nasal polyps) from both groups were obtained and processed with Hematoxylin-Eosin (H&E) and gram staining. Specimens from the ultrasound-treated group received low frequency ultrasound (1 MHz, 1.0 watt/cm2, 20% pulsed mode, for 5 minutes at 370C) post-extraction and prior to staining. In phase II, the ultrasound group also received the same ultrasound treatment while the control group underwent ultrasound at 0 MHz frequency, 0 watt/cm2, both twice a week for 3 weeks, beginning one (1) week post operatively. Both groups accomplished SNOT-22 forms and were evaluated via modified Lund MacKay endoscopic appearance at 1 week (week 0 of treatment), 2 weeks, 3 weeks, and 1 month post operatively (week 3 of treatment). Results: Paired T-test showed a statistically significant difference between control and treatment groups in epithelial thickness with a p-value of 2.29E-10 (average of 73.34um for controls and 31.1um for the treatment group) at 95% confidence interval. The inflammatory cell count also differed significantly between control and treatment groups (average 293.85 and 29.65 inflammatory cells per high-power field in 10 random microscopic fields, respectively), p-value of 1.05E-17 on paired T-test; CI 95%.  In phase II of the study, SNOT-22 results showed significant differences in improvement of symptoms in ultrasound-treated patients after Endoscopic Sinus Surgery (weekly mean scores of 38.05, 21, 11.3, and 10.45) and in modified Lund Mackay endoscopic appearance scores (weekly mean scores of 7.88, 4.35, 3.02, 2.08). Two-way analysis of variance showed significant differences between control and treatment groups for both SNOT-22 (p = 1.07E-80; 9.71E-119; CI 95%) and modified Lund Mackay endoscopic appearance scores (p = 3.89E-60; 1.85E-95; CI 95%). Conclusion: Low frequency therapeutic ultrasound demonstrated possible efficacy as an agent in disrupting epithelial architecture in patients with CRS-NP as well as in symptom improvement after endoscopic sinus surgery patients based on histopathologic evaluation, SNOT-22 and modified Lund MacKay endoscopic appearance scores. Low frequency ultrasound may be an adjuvant to conventional medical treatment in CRS-NP. Keywords: Biofilm, Sinusitis, Nasal Polyps, Chronic disease, Ultrasonic therapy