We document implementation and enforcement activities undertaken by high schools and health units with regard to the 1994 ban on smoking on school property in Ontario. Telephone interviews were conducted in the early summer of 1996 with 213 high school administrators and 38 tobacco enforcement personnel in health units. While some schools are unclear about enforcement responsibility, most are making efforts to enforce the ban, including warning and suspending students. Some school administrators (30%) suggest the reinstitution of designated smoking areas on school property. One quarter of health units had not made enforcement visits in schools in the 1995-96 school year and a minority accounted for most of the warnings and tickets issued to students. While most tobacco enforcement officers perceive that schools support the ban, they report some problems in obtaining cooperation in enforcement. However, only 11% suggest returning to designated smoking areas on school property.