The epidemic of Asian influenza in the United States was preceded by a period of 3 months when sporadic cases and localized outbreaks were frequent but did not lead to community-wide spread. True epidemic prevalence began in mid-September. The peak was reached in late October and the epidemic had largely subsided by late November. A "second wave" of excess pneumonia mortality occurred during the late winter and spring. From the first identification of the new, antigenically-variant strain as the cause of the Far Eastern epidemics, epidemiologists were almost unanimous in predicting a global epidemic. These predictions came true. There was no agreement on the severity of the epidemic nor on the character and extent of the "second wave", the cause of which remains an enigma. The epidemiologic pattern of the 1957 pandemic of Asian influenza resembles in many respects the 1918 pandemic and in even more respects the 1889-91 pandemic, but it is strikingly different from the pattern of the last major antigenic shift which occurred in 1947.