During 1966, 678 known individuals became ill with malaria in the United States and Puerto Rico. This is the largest number of cases for any year since 1954. This increase was due primarily to the 538 cases of malaria in returning U. S. military personnel who were infected in Vietnam. Civilians accounted for 115 cases, of which 30 occurred in former Peace Corps volunteers.I. SUMMARY -- II. TERMINOLOGY -- III. GENERAL SURVEILLANCE INFORMATION -- IV. MALARIA IMPORTED FROM VIETNAM -- V. MALARIA ACQUIRED IN THE UNITED STATES -- VI. DEATHS DUE TO MALARIA -- VII. MALARIA SURVEILLANCE REVIEW, 1957-1966 -- VIII. REPORT FROM THE NATIONAL MALARIA REPOSITORY -- IX. ACKNOWLEDGMENT -- Figure I. Reported malaria in the United States, 1933-1966 -- Figure ...