The results of a special survey of cancer mortality statistics in selected areas of the Ober- and Unterland of Württemberg in the period 1908--1912 were compared with the official mortality statistics of the same region for 1969--1972. In the Oberland, formerly part of an area of high cancer mortality comprising the adjacent regions of Bavaria, Austria, Switzerland, and Baden, the overall cancer mortality showed a marked fall in both sexes. In the Unterland, where cancer mortality was previously low, the overall death rate increased in men and did not change in women. These variations are largely accounted for by changes in mortality from cancer of the stomach and bronchus. The death rates from gastric cancer observed around 1900 in the Oberland of Württemberg and adjacent regions of the neighbouring countries are among the highest recorded even in the world. Since the fall of gastric cancer noted is very marked and this disease is still the leading cause of death from cancer today, the Oberland of Württemberg seems to be uniquely suited for the search of environmental factors which associate with this decline. In theremainder of cancer sites changes over time were less striking and/or observed already in other countries.