In a rural population-basod cohort study of approximately 500 Gambian children under five years old followed for one year, incidance of acute lower respiratory infection(ALRI) was related to various risk factors including parental smoking and regular carriage on the mother's back while cooking. a apoxy measure for exposure to smoke from cooking fires. Two statistical analyses using a ‘child-weeks at risk’ approach were carreid out, including and excluding multiple disease episodes in the same child. weekly suveillance for ALRI found 75 episodes in 62 children. Stratified analyses using both approches suggested father's smoking, and, for girls only, carriage on the mother's back while cooking and being part of a polygamous family were the main risk factors associated with infection: when multiple episodes occurring in the same child were excluded, not having a health both approaches, including each of these risk factor and sex, age, village and season, suggested father's smoking, cariage on the mother's back while cooking and being part of polygamous family increase risk of ALRI, the latter two for girls only. The analysis excluding multiple episodes in the same child also suggested that not having a health card is risk factor for children aged 1–5 years. The difficulties in interpreting these findings are discussed.