Clean indoor air (CIA) ordinances in Toledo, Ohio, and Bowling Green, Ohio, regulate smoking in restaurants to protect patrons and employees. Yet complete protection is questionable because the ordinances allow for smoking in certain dining sections. Two restaurants were studied in each city, one smoking and one nonsmoking. Levels of contaminants related to environmental tobacco smoke (ETS)--determined by personal and area air monitoring-in the nonsmoking restaurants were comparable to levels in a control environment. However, levels of ETS-related contaminants in the smoking restaurants, including designated nonsmoking sections, were significantly higher than levels in the control environment. ETS-related contamination of the nonsmoking sections in the smoking restaurants is attributable to direct openings between the smoking and nonsmoking sections. Reasonable protection of employees and patrons against ETS-related contaminants requires strict enforcement of CIA ordinances. Full protection is achievable only with 100% smoke-free policies.