Abstract: This patent relates to ergonomically correct seating during long periods of time, especially for professionals who work with hands extended like dentists and hand surgeons, but also computer users and other office or assembly workers. While the immediate comfort is provided by the shape of the seat and the backrest and by the upholstery, the long time comfort is determined by proper sitting posture. Comfortable sitting posture is individual and requires a large range of adjustments for height, seat inclination and the positioning of the back support relative to the seat. Recognizing the importance of these adjustments—not only for comfort but also for avoiding back problems—this adjustment mechanism is designed to accomplish all three adjustments with a single lever. The mechanism is designed for use with the lever mounted on the right side or the left side of the chair to accommodate personal preferences.