Summary Problems of malaria eradication are discussed in terms of relevant human ecological factors. Principal human factors seen as related to the success or failure of malaria eradication programs are: poverty, ignorance, illiteracy, social deprivation, migration and local mobility of populations, differential exposure of populations to Anopheles mosquitoes, alterations in the physical environment associated with development programs, cultural attitudes toward mosquitoes and malaria, and population-malaria program relationships. It is suggested that as malaria eradication programs progress, the relative importance of human factors in determining their effectiveness is likely to increase.