BACKGROUND Over the past 15 yr, remarkable progress has been made in the development of touring motor gliders and self-launching sail-planes with retractable propulsion units (RPU gliders.) Annually, over 50% of the gliders produced have had such units, often two-stroke engines which produce high frequency sound emissions. Sound emission regulations require that all power gliders be insulated to avoid external emissions and noise pollution in the airspace near airfields. However, these regulations do not cover noise within the cockpit. METHODS To determine the noise level in the cockpits of powered gliders and how this noise affects the hearing of pilots, cockpit noise in six touring motor gliders and nine RPU gliders were measured. RESULTS Both types of motor gliders have noise levels that may be hazardous to pilots' hearing if they are not equipped with personal noise protection. In extreme cases an exposure time of only 20 seconds to the cockpit noise of an RPU glider may cause permanent hearing loss. CONCLUSION Pilots must be warned not to fly motor gliders without personal noise protection.