Cautery-assisted palatal stiffening operation (CAPSO) is a recently developed single office-based procedure performed with local anesthesia for the treatment of palatal snoring. A midline strip of soft palate mucosa is removed, and the wound is allowed to heal by secondary intention. The flaccid palate is stiffened, and palatal snoring ceases. This prospective study evaluated the ability of CAPSO to treat obstructive sleep apnea syndrome (OSAS). Twenty-five consecutive patients with OSAS underwent CAPSO. Responders were defined as patients who had a reduction in apnea-hypopnea index (AHI) of 50% or more and an AHI of 10 or less after surgery. By these strict criteria, 40% of patients were considered to have responded to CAPSO. Mean AHI improved from 25.1+/-12.9 to 16.6+/-15.0 (P = 0.010). The Epworth Sleepiness Scale, a subjective measure of daytime sleepiness, improved from 12.7+/-5.6 to 8.8+/-4.6 (P<0.001). These results indicate that CAPSO is as effective as other palatal surgeries in the management of OSAS.