In the 1930s he became a noted public debater. He issued the 1934 book "Rasepolitikk og reaksjon", and wrote with the purpose of medicinal and hygienic enlightenment in the publications "Populært Tidsskrift for Seksuell Oplysning" (which he edited) and "Arbeidermagasinet". He was also a popular radio speaker and lecturer. In 1938 he was appointed to the vacant position as director of the Norwegian Directorate for Health. When World War II came to Norway, Evang followed the cabinet Nygaardsvold first to Northern Norway, then to exile in the United Kingdom. Evang was given the rank of lieutenant colonel. He spent the war years organizing a health administration for Norwegians abroad, spending time in the USA as well. After the war he co-founded the World Health Organization; he was also board chairman for some time. His position was strengthened after the war, and Evang signalized technocratic ambitions. Similarly, the health conditions in Norway improved in the post-war years. Poliomyelitis was eradicated and tuberculosis diminished. However, several welfare programs were implemented long after Evang's initiatives. He also had political ambitions (Minister of Social Affairs, probably also Prime Minister) that were never fulfilled.