A critical overview is presented of selected findings from a series of case-control studies conducted in the greater Milan area on cancers of the digestive tract, breast, female genital tract, prostate and bladder. Even using very simple data collection instruments (based on the frequency of use of a restricted number of food items), a number of consistent and strong associations emerged. In particular, frequent green vegetable consumption appeared to exert substantial protection against most of the cancer sites considered, which could not be explained in terms of information, selection or confounding bias. Other interesting clues, such as a moderately positive relation between fats and breast cancer, and a positive association between maize and esophageal or gastric cancer are discussed in order to illustrate the potential scope of studies of diet and cancer risk based on populations with considerable heterogeneity and modifications in dietary patterns, and recent changes in mortality from various common cancers.