This paper reports data on changes in smoking behaviour after the introduction of a total workplace smoking ban in Telecom Australia. A sample of 1089 Telecom staff were surveyed in the months before the introduction of the ban and 620 were resurveyed six months after the ban had been implemented. A further sample of 1424 was drawn from the same parts of the organisation 18 months after implementation. Among the smokers in these samples, the bans produced a reduction in workday cigarette consumption of between three and four cigarettes a day and this reduction was maintained at 18 months. Over the two-year period from six months before the ban to 18 months after it, smoking prevalence dropped about 5 per cent, which we estimate is about twice the decline found in the general community. Workplace smoking bans can produce public health and can assist individual smokers to regulate their habit.