Clustering of disease is intriguing and some cluster investigations have led to important scientific discoveries. For example, investigation of the spatial clustering of enamel discoloration early in the 20^th century led to the discovery of the relation between flouride levels in drinking water and dental caries.

Most cluster investigations focus on cancer. Many carcinogens have been discovered through occupational or medical cluster investigations. Many neighborhood cancer clusters have been reported (most often for leukemia and/or lymphoma); to date, no clear-cut etiologic relationships have been established.