The official dialogue between the Roman Catholic Church and Classical Pentecostal representatives is the only substantial bilateral dialogue between a historic church and a 'young' spiritual movement. In view of the challenge of ecumenism in the twenty-first century to incorporate new expressions of Christian community life into the ecumenical movement, this dialogue offers us an interesting test case. Since its establishment in 1972, it has gone through five phases of dialoguing, each lasting five to nine years. Both the Final Reports on each phase and the comments given by participants and observers throughout the last 35 years show the inner dynamic of this unique dialogue. It was based on a simple friendship and started as a long series of exploratory meetings with little theological but much relational gain. Yet slowly but surely it evolved into a strong dialogue that is characterised by a recognition of spiritual unity, a deep mutual respect, and an ability of honest self-criticism, teaching us that the new ecumenism requires the basis of a loving relationship and courage to leave the well-trodden paths.