The purpose of this research was to identify the conditions of successful implementation of the universal, school drug primary prevention programme, Walk Tall, in Irish primary schools. This research relied on the expert views of Irish primary school teachers, who are at the front line of the delivery of the Walk Tall programme. Data was collected by means of interviews of ten primary school teachers and by questionnaires. The study aimed at establishing the validity of three main hypotheses: the characteristics of schools and schools daily life, the teachers' perceptions of the primary school curriculum and the socio-cultural characteristics of schools' environments influence successful implementation of the Walk Tall programme in Irish primary schools. Each main hypothesis was divided into several sub-hypotheses in order to refine the research. The definition of success, suggested by most teachers, in relation to the implementation of the Walk Tall programme, was to equip pupils with the necessary self-esteem and decision making skills before starting secondary education. In relation to the first hypothesis, findings established that the reality of schools' facilities, a high proportion of children of foreign parents within the schools and the existence of extra-curricular activities within the schools could have a negative influence on the successful implementation of the Walk Tall programme, while parents' involvement in school life could favour it. It was also established that schools' status, the implementations of a school substance misuse policy, targeted programmes and ad hoc interventions within the schools did not influence positively or negatively successful implementation of the Walk Tall programme. Regarding the second hypothesis, the study concluded that the primary school curriculum, perceived as overcrowded by teachers had a negative impact on successful implementation of the Walk Tall programme, while the good quality of the programme as a pedagogical tool and structured working relationship among schools' staff acted as positive factors for successful implementation of Walk Tall within primary schools. Finally, in relation to the third hypothesis, the study established that school locations within a Local Drug Task Force area or a disadvantaged area did not impact significantly on successful implementation of the Walk Tall programme. The same conclusion was reached for the presence of significant misuse within the schools' environments as well as schools' locations in inner-city or suburban settings. However, considering that none of the schools located outside the Greater Dublin area have implemented the Walk Tall programme, it was possible to state that a location outside Dublin or any other Irish cities, may influence the absence of successful implementation of the Walk Tall programme.