The paper reviews the early toxicologic and pharmacologic studies carried out by the author and his associates from 1943 to 1947, which were largely responsible for launching DDT as an agent for the control of typhus, malaria, yellow fever, and related vector-borne diseases. After reviewing recent studies conducted at the University of Miami, which dealt with organochlorine pesticides in human tissues, the tumorigenicity of aldrin, dieldrin and endrin (rat), six-generation mouse and three-generation dog reproduction studies, synergism of DDT and aldrin (dog), and the fate of DDT and aldrin during a period of severe starvation (rat), it is pointed out that it is primarily the overuse and misuse of DDT in pest control that have caused the pollution in our ecology. It is emphasized that the requirements for pest control differ the world over and that it must therefore be left to the national regulatory agencies to legislate the safe use of DDT and related pesticides. It is recommended that future human and animal studies with DDT and its derivatives give consideration to: (a) the balance and metabolism of the various hormones, (b) reproduction (estrus, libido, mammary development, milk production, (c) hepatic microsomal enzyme activities, (d) cancer prevention and cancer production, (e) excessive body weight changes induced by disease, unbalanced diet or starvation, and (f) the effects of DDT and its derivatives when absorbed in combination with other related and even unrelated compounds.