Chiefly in the Netherlands, a decrease in the number of births and infant mortality began around 1875-1880; the so-called demographic transition. This decrease continued well into the 20th century. This article examines which methods of contraception were used during this period. The Dutch ‘New Malthusian League’, founded in 1881, advised its members on methods of contraception. The most important methods were coitus interruptus, vaginal douches, vaginal sponges, the diaphragm and condoms. A large majority of physicians were opposed to birth control until the 1950s. Hector Treub, professor of gynaecology in Amsterdam, was one of the few advocates of birth control. Research in the 1960s, carried out just before the introduction of oral contraceptives, revealed that in Amsterdam by far the most popular method in use at the time was coitus interruptus. The conclusion is that this method will have made the most important contribution to the decrease in births.