Therapeutic ultrasound, an important physiotherapy modality, has been used successfully in the treatment of patients with chronic rhinosinusitis (CRS). No study has compared pulsed ultrasound (PUS) with erythromycin phonophoresis (EP). The aim of this randomized, double-blind, parallel group study with concealed allocation was to compare PUS with EP. Sixty CRS patients were randomly allocated into two groups. Group 1 had PUS and Group 2 had EP. Patients were treated 3 days a week for 10 sessions over 4 weeks. The severity of nine CRS symptoms was self-rated by patients on an ordinal scale of 0-3 (absent, mild, moderate or severe) at baseline and after the 10th treatment session. Individual symptom scores were summed to obtain a "Total Symptom Score" (TSS). The outcome measure included percentage improvement in the TSS. A statistically significant improvement in TSS occurred with both PUS and EP therapy groups (p < 0.05). The percentage improvement in the EP group was statistically greater than in the PUS group (67.2 versus 49.3%) (p = 0.03). The effect sizes in both therapy groups were large; PUS: d = 1.36 and EP: d = 2.15. EP was found to be superior over PUS therapy.