Toward the end of January, 1920, when the recurrent epidemic was at its height in Boston, the author undertook with the aid of thirteen trained social service workers, and one physician, who was a graduate of the Harvard School of Public Health, to make a sickness census of 10,000 individuals. Six districts were chosen in different sections of the city, representing six different economic and social groups. Great care was exercised in selecting the districts, so that the population in each might be as homogeneous as possible regarding economic and sanitary status, as well as race, and living conditions in general. We have sought to clarify and to abbreviate our description of the characteristics of the various districts by incorporating a map, together with photographs of typical streets in each district. One who compares these streets as they are seen in the photographs would scarcely find it necessary to enter the buildings in order to discover the living conditions of the occupants (Chart XIII). CHART XIII. [Illustration: Map of greater Boston showing the distribution of the districts covered by the author’s house census. ] District I includes an Italian population of 2,000 individuals, one-half of which live in the most congested portion of the city (see photograph) known as the North End, while the other half, living in East Boston, are slightly less crowded. District II, in South Boston, consists of 2,000 individuals almost entirely of Irish race stock. [Illustration: FIG. 1.—District 1. Italian tenements. Very congested and very poor. ] District III, like District I, consists of three groups living in very similar environment to the two groups of the first district, but composed chiefly of Jewish race stock of various nationalities. The photograph for this district represents the area in the “West Side” near the Charles River Basin. The area in the “South End” is of similar type, while the area in East Boston is housed similarly to the Italian district in East Boston. The dwellings in both of these latter districts correspond to those shown in the second photograph of District II. While the first three districts comprise tenement areas, some poor and the remainder very poor, Districts IV and V represent the middle class, and consist nearly entirely of “Duplex” and “Three-Decker” buildings. The first of these comprises 1,000 individuals of mixed race and nationality, the type broadly spoken of as American. The second consists of a Jewish population of 1,600. [Illustration: FIG. 2.—District 2. Irish tenements. Congested and poor. ] [Illustration: FIG. 3.—Another street in the Irish tenement district. ] [Illustration: FIG. 4.—District 3. Jewish tenements. Very congested. Very poor. ] [Illustration: FIG. 5.—District 4. Middle class. Mixed American population. ] [Illustration: FIG. 6.—District 5. Middle class. Jewish population. Moderately well-to-do. ] [Illustration: