Science, in one of its meanings, is co-ordinated and systematized knowledge. Co-ordination and system imply classification, and it is useful occasionally to spend a little time in preparing or testing systematic groupings of the various phases of a given specialty. Exhaustive and organized lists of this sort may lead to clearer understanding of both extent and limitations of a subject, orienting one's thinking and perhaps suggesting lines of experimentation. Classifications of measures of malaria prophylaxis and mosquito control have been few and not very satisfactory. The material for this paper has been developed over a period of years and is based partly on studies published by Russell (1934), by Russell and Hackett (1938), and by Hackett et al. (1938). It is an attempt to prepare a systematic list in which every recently suggested measure is included in its logical place.