OBJECTIVE To examine the relationship between tobacco smoking, oral hygiene, gingival and periodontal health in young adults. METHODS Cross-sectional (conducted in the course of a cohort study). METHODS Cardiff, UK, 1989 and 2000. METHODS Plaque was recorded, as was presence or absence of bleeding on probing and loss of attachment (LA). Information concerning tobacco smoking was obtained from questionnaire data. RESULTS At age 19-20 years, smokers had statistically significantly (P < 0.01) higher whole mouth mean plaque scores than non-smokers. Whole mouth mean bleeding scores, however, were similar in smokers and non-smokers. The relationship of plaque to smoking was very similar at age 30-31, yet bleeding scores were approximately 25% lower in smokers than in non-smokers (P < 0.01). Whole mouth LA scores showed small, statistically non-significant differences between smokers and non-smokers. At the age of 30-31 years, gender and social class had a negligible confounding effect on oral hygiene, gingival and periodontal health in smokers and non-smokers. CONCLUSIONS Smokers consistently demonstrated poorer oral hygiene than non-smokers. The effect of smoking in reducing gingival bleeding was already apparent at age 19-20 years despite the fact that, at this time, subjects might be assumed to have been exposed to a relatively small dose of tobacco over a short period of time. In the follow-up study conducted at the age of 30-31 years, the impact of smoking on the periodontal tissues was, as expected, more pronounced.