To determine whether smoking contributes to the risk of primary intracerebral haemorrhage (ICH) a case-control study was carried out on 331 consecutive cases of first-episode ICH as verified by computed tomography. Patients were age- and sex-matched to 331 community-based controls. Unlike other forms of stroke where smoking is an established risk factor, there was no increase in risk of ICH with smoking in this study (odds ratio, OR, 1.07, 95% confidence interval, CI, 0.631.81). Similar ratios were obtained for past and current smokers. Neither the amount smoked nor the duration of smoking were associated with ICH. Further investigation, however, revealed an interaction between smoking and hypertension on the risk of ICH that was similar regardless of the amount of cigarettes currently smoked and was largely seen to be a phenomenon in men (OR 8.13, 95% CI 2.0432.42). This interaction is a new finding, but the post-hoc nature of this analysis requires that it be further tested, preferably in a large prospective study.