Control of communicable diseases is the major public health challenge in all southeast Asian countries. Unless public health activities are strengthened at grassroot level, control of communicable diseases is not possible. Of them, Tuberculosis, Malaria and HIV/AIDS are documented to be the most prominent public health problems that account for high rates of morbidities and mortalities. Community health workers must be adequately trained to understand their role in control of these diseases. Application of principles of public health with co-ordinated efforts in right direction is the key to success of control programme of said diseases. This document has explained about health & diseases, causal factors of diseases, measuring health status of a community,levels of disease prevention, public health approach and indicators for disease control etc. It has also described epidemic investigation, field survey and role of health workers in different field situations. Malaria, TB & HIV/AIDS have been described considering public health aspects of these diseases and how to approach for controlling them in a defined geographical area.