A comparison has been made between 393 indigent Missourians with multiple primary cancers of different tissues and 100 with single primary cancer. The 2 groups are sufficiently similar in all features tested (except religious practice) that it is impossible to predict a cancer proneness in any. The findings show that each new neoplasm is best recognized early for most effective salvage. Merging the sites of involvement in the Missouri sample with others from the medical literature resulted in a collection of 4,271 site‐pairings of multiple cancer. These data suggest that, when cancer first appears in certain tissues, some tissues then have a greater, and some a lesser, likelihood of developing second neoplasms if cancer does begin a second time. This information can be helpful in the care of persons who have had cancer if those tissue zones deserving particular attention in follow‐up are emphasized.