John Terence was the son of Henry Cahill, a medical practitioner. His brothers, Frank and Harry, were a surgeon and a general practitioner.

He completed his secondary education at St Patrick's College East Melbourne and graduated in 1940 from the University of Melbourne with first class honors and with exhibitions and prizes in both medicine and surgery. In 1946 he completed his Doctorate of Medicine and was admitted to MRACP. He then travelled to London for further experience in medicine and in particular cardiology.

He became physician to outpatients at St Vincent's Melbourne in 1950 and in 1965 became Physician to inpatients. Throughout this time he was in consulting practice which he ceased in the mid 1990s.

He had many notable positions at St Vincent's Hospital. He was Chairman of the Senior Medical Staff in 1968, Chairman of the Division of Medicine from 1975 to 1977, a clinical instructor in medicine at The University of Melbourne from 1950 and a member of the examining board in the Faculty of Medicine from 1952. He was a member of the Australian Medical Examining Council which assessed the credentials of foreign medical graduates seeking registration in Australia.

He was also a commonwealth medical referee giving final opinion in medical cases involving public service and members of the armed services. He was Chief Medical Officer for a large number of insurance companies in Australia.

He was a tall, handsome man, charming in all respects and regarded as very helpful to his patients. He was frequently the doctor's doctor.

His first wife Eileen died in 1969. He then married Christine who survived him. He had one son, John, who predeceased him and he was survived by two daughters, Bernadette and Gabrielle, 6 grandchildren and 1 great grand child.

He loved company and travel, particularly for pleasure, and attended many overseas conferences.