The paper describes a dental health education program designed to modify the oral hygiene behaviour of a selected group of women in their first pregnancy. The study group were exposed to a lay educator with a program which was directed at the behaviour, rather than the knowledge or feelings of each individual in the group. Results were estimated by using oral hygiene effectiveness scores. The study group showed a 38 per cent reduction in mean scores after 12 months, significantly greater than the 18 per cent reduction shown by the control group. This represents a considerably improved clinical picture. Main conclusions are that primigravida are a worth while target group; that a carefully chosen lay health educator may be an effective teacher and a program which provides intermittent feed back and support may establish better health habits.