ABSTRACT Literature has shown that knowledge of environmental sanitation helps in the promotion of individual and community health practices. Health education modifies peoples' behaviours such that it can have a great impact on national development. This study investigated the influence of the knowledge of environmental sanitation as it relates to health behaviours of school adolescents in Lagos State. Study adopted descriptive survey research design. Two hundred secondary school adolescents were sampled, using stratified and systematic sampling procedures. Three research hypotheses were tested at 0.05 alpha level. Questionnaire was validated and subjected to the reliability coefficient of 0.77. Data were analysed using Chi- Square statistics. There were significant impacts on 2 2 personal hygiene practices (X = 183.21,, p < 0.05), classroom cleanliness (X = 191.12, p < 0.05) and food hygiene 2 practices (X = 107.21, p < 0.05). There is need for health officials to be visiting secondary schools in order to promote enlightenment on environmental sanitation among secondary school students in Lagos metropolis. Aaron O. Akinloye Department of Human Kinetics and Health Education University of Lagos University Road 101017 Akoka, Yaba, Lagos State, Nigeria ERA’S JOURNAL OF MEDICAL RESEARCH COGNITIVE ENVIRONMENTAL SANITATION ON HEALTH PRACTICES OF SECONDARY SCHOOL ADOLESCENTS VOL.6 NO.1 Original Article Page: 1 ERA’S JOURNAL OF MEDICAL RESEARCH, VOL.6 NO.1 Dr. A. Akinloye Department of Human Kinetics and Health Education, University of Lagos University Road 101017 Akoka, Yaba, Lagos State., Nigeria Email: akinloyeaaron@gmail.com Contact no:+234-8037168893 Address for correspondence Received on : 06-04-2019 Accepted on : 10-05-2019 KEYWORDS: Environmental sanitation, Health practices, Adolescents. INTRODUCTION Health appreciates every day and depreciates every day, which leads to its variation from time to time, but a balance of it makes individuals to assume being healthy. Turner reported that, those with least state of health, value health the most, and that children at the age of ten to eleven, tend to ignore personal hygiene (1). This is to say that, without the adequate provision of health knowledge, these children would relatively be dirty, and giving room for communicable diseases to spread. Dare said “our school surroundings are weedy, littered, inadequate sanitary facilities, and ill ventilated, resulting to the outbreak of communicable disease among children who are the future leaders of the country” (2). He added that the inspection of students' finger nails, hairs, and school uniforms on the assembly lines every morning no longer happens. The teaching of personal hygiene has been eliminated from time table in most schools and that students have developed unhygienic health habits inimical to good health practices Infectious and parasitic diseases associated with low standards of sanitation remain the leading cause of morbidity and mortality in many developing countries (3). Human environmentally related diseases such as malaria, typhoid, diarrhea and dysentery are a constant threat to life (4). Lack of potable water supply and poor environmental sanitation are the reasons diseases associated with unhygienic disposal of human faeces and refuse are so common in developing countries. The most important of such diseases are diarrhea and intestinal worm infections which account for over 10% of the total disease burden in developing countries. Inadequate supply of potable water increases the risk of schistosomiasis, guinea worm and skin infections (5). These environmentally related diseases can be controlled and prevented through health promotion and improvement in environmental sanitation (6). Health promotion aims at increasing the host's ability to withstand stress in the environment such as through good nutrition and health education. The objective of environmental sanitation is to create and maintain conditions in the environment that will promote health and prevent diseases. This can be achieved through minimizing pollution of water, air, and soil; and by having a good focus on other measures of environmental sanitation that will reduce the transmission of communicable diseases to children and adults. Stubbs, explains that health is being threatened by air, water, and food pollution, and are in danger of being engulfed in trash (7). Unless children have adequate health knowledge of how one's carelessness could endanger self and others, the above problem as it is manifested now in our unhygienic environment, will increase our being engulfed in the trash. Therefore, the EJMR