A method of diagnostic reasoning that states one should look for diseases where they are most likely to be (e.g., malaria in tropical areas that harbor Anopheles mosquitoes; atherosclerosis in patients who are smokers, hypertensives, or diabetics). The law is attributed to Willie Sutton, a U.S. bank robber, who, when asked why he robbed banks, said, “Because that’s where the money is.”