Endel Tulving was best known for his experimental studies of human memory, and the conceptual distinctions he introduced. He found techniques to demonstrate the presence of stored information - accessible by special tests - that could not be revealed by other tests, and to show the internal organisation of memory material within the person. From these results, he deduced the importance of the particular code created by the person during original experience, and of the access to that code provided by the conditions of recall or recognition. He also distinguished memory for individual events or 'episodes' from that for lasting 'semantic' relationships. His methods and distinctions were increasingly finding application, not only to theories of memory, but to the analysis of the effects of brain injury.