Kaare Nygaard started his medical studies at the University of Kristiania (Oslo) in 1922.  Summers he worked for surgeon and chief of staff Olav Tandberg at the County hospital at Lillehammer.  Dr. Tandberg was a great support for Kåre throughout his studies and later also in the USA.

During his student days, in 1927, he met Ella Frey, a physical therapist, who later was to be his wife.  Kaare fell promptly, and the feelings were reciprocated.  They got engaged the next year, and married in Chicago October 10, 1933.  There were no children in the marriage, and Ella passed away after 43 years of marriage in 1976.  He later re-married to Gail Delgado.

Kaare was graduated from the University of Oslo in 1929, and awarded his authorisation as a doctor January 3, 1930.  After a short period as a district doctor, he left for the USA in May 1930 to specialise as a surgeon.  He went to the Gundersen clinic in La Crosse, and started writing his name in the English way: Kaare K. Nygaard.  The Gundersen Clinic had a name as a medical center, but also as a milieu where Norwegian culture was treasured.  Dr. Nygaard enjoyed this environment where each day brought new education.  He matured, both as a doctor and as a person.

A year and a half later he was offered a position as an assistant surgeon at the Mayo Clinic in Rochester in October, 1931.
Dr. Nygaard excelled, both as a surgeon and a researcher.  His most important research work was done at the Mayo Clinic and completed in 1935.   In it he compared spinal anesthetic to ordinary anesthetic.  He started researching the ability of blood to coagulate and its tendency to form blood clots, a matter that was in its early stage at this time.

Kaare Nygaard stayed at the institution for the next five years, and the Mayo Clinic became a place that he often would return to.

To show his gratitude, he later gave his statues "Cancer" and "The Surgeon" to the clinic, as well as a mobile work of art by Alexander Calder.

After six years in the USA, Nygaard returned to Norway.  He was employeed at the Rikshospitalet (National hospital).  Dr. Nygaard brought a lot of new knowledge from the USA, and he willingly shared.  On a model from The Mayo Clinic he introduced staff meetings, weekly meetings for the medical staff where important medical questions could be discussed.  To this day, these are common procedure at most Norwegian hospitals.

To complete a dissertation on bleeding deceases, he returned to the Mayo Clinic in February of 1940.  It was finished in the summer of 1940 and published the next year.
This year he also established a private practice at the White Plain Medical Center, in the town of White Plains northwest of New York City.  This was the beginning of a career that was to last for 39 years, and that brought him a reputation as one of the most competent surgeons in the state of New York.