Lessons from Mackenzie that still resonate.

INTRODUCTION Sir James Mackenzie (1852–1925) is known as ‘the father of general practice-based research’.2 From humble origins in rural Perthshire, Mackenzie overcame early social and educational hurdles to study medicine in Edinburgh, then pursued a career in general practice in Burnley. He initiated the systematic observation of his patients that led to his stellar research career, including an international reputation in cardiology, discovery of novel and important insights into heart rhythms, the use of digitalis, and a knighthood. At the height of his career in London, he returned to establish the Institute for Clinical Research in St Andrews at the age of 64. It was there that Mackenzie brought together all the GPs working in the town, and encouraged the systematic recording of routine observations and the development of record-keeping systems. By working with local colleagues in primary care, he made his real key insight: that systematic observation and recording of symptoms and signs in a whole population could provide essential information on the epidemiology, prognosis, and mechanisms of disease. Common themes and lessons still echo from his paper,3 highlighting issues that were as important and controversial in 1921 as they are today.