Indigenous Indonesian Catholics increased in number from 27,000 to nearly 550,000 between 1902 and 1942. At first scattered only through Minahasa, the Kai islands and Flores, after four decades Catholic centres were established in most of the archipelago, and there was even a small but well-educated and vocal minority in Central Java. It is this formative period in the growth of Catholicism in Indonesia that Steenbrink describes in detail. Catholics never constituted more than three per cent of the Indonesian population, one-third of all Christians. Steenbrink examines the rivalry of this minority with Protestants and their missionary activities, as well as the race with Islam in many parts of the outer islands, which had come under Dutch rule in the early twentieth century. This comprehensive work includes extensive details on the different European missionary orders and missionaries active at this time.