The relationship between the respiratory system and the environment involves a complex dynamic interaction of genetic susceptibility, host defence and toxicity. The chance of an individual developing a respiratory disease is dependent on genetic susceptibility and subsequent hereditary risk factors, life-style risk factors and the amount and nature of the exposure that may be encountered in the working environment. Atopic status is an important pre-existing risk that a worker may bring to the workplace (occupational asthma/rhinitis to high molecular weight agents). Smoking is an avoidable additional risk for certain occupational diseases (occupational asthma/bronchitis/cancer) while it can be protective in other circumstances (allergic alvcolitis). More controversially, smoking in some workers may put at increased risk the health of colleagues (passive smoking). This article attempts to clarify the issues surrounding the interaction of atopy, smoking and the workplace.