Urban growth in the developing world is likely to be accompanied by health problems in crowded zones where services are not available. Geographical analyses of aggregated data may prove interesting, but reliability and utility of spatial correlations are greater when microscale data are acquired. In this study data for households in 11 Jakarta neighborhoods were collected in interviews. Malaria and diarrheal disease patterns have been correlated with environmental and socioeconomic variables at the household level. Several environmental characteristics seem to be closely associated with the incidence of malaria and diarrheal diseases.