The relationship between dentine lead levels and maternal/teacher ratings of inattentive/restless behaviour in children was examined for a birth cohort of New Zealand children. There were small but relatively consistent and stable correlations between dentine lead values and behaviour ratings. After correction for errors of measurement in dentine lead values and behaviour ratings it was estimated that the correlation between lead levels and inattentive/restless behaviour was in the region of +0.18. However, after control for various sources of confounding there was only a small, but statistically significant, correlation of +0.08 between lead levels and inattention/restless in children. It is concluded that the weight of the evidence favours the view that there is a very weak causal association between lead levels and attention and activity levels in children.