From 1924 onwards, mandatory tuberculin testing (von Pirquet's method) was introduced for student nurses on entry to the Ullevaal Hospital School of Nursing, Oslo. The chief physician of the hospital's Department IX, Olaf Scheel, was responsible for this measure. In 1927, his deputy Johannes Heimbeck showed that about half of the students were not infected at the time of entry, a conclusion that was in fundamental conflict with the prevailing view that nearly all tuberculous infection occurred in childhood. Virtually all tuberculin-negative student nurses, however, became infected during their 3-year training. These findings changed our understanding of the pathogenesis of tuberculosis. BCG vaccination had recently been introduced by Calmette. From 1927 onwards Heimbeck offered BCG vaccination to tuberculin-negative student nurses, while Scheel undertook a similar project among medical students. The two projects continued until respectively 1936 and 1939. Long-term follow-up of both groups demonstrated a protective effect of about 80% in those accepting vaccination. Calmette had given the vaccine per os to new-born babies. Heimbeck and Scheel pioneered giving the vaccine via injection and to adults. These projects have been criticised for being based on voluntary inclusion and not being conducted as randomised control trials. The results were so convincing, however, that they led to the launch of the Norwegian BCG programme shortly after World War II. Scheel and Heimbeck' efforts were also of great importance for the use of the BCG vaccine in other countries.