Vuelta a Alemania
Post turned professional in 1956 with the small Dutch team R.I.H. He rode for the first few years with Gerrit Schulte, a track rider who also rode on the road and was an inspiration to him. Notable early career successes on the road came when he won the Ronde van Nederland in 1960 and the 1962 Deutschland Tour. In 1963 he became national road race champion as well as winning the Tour of Belgium.