ObjectiveTo determine risk factors for chronic periodontitis in 30–60 year olds in Sri Lanka. Cases and controls for this population based unmatched case–control study were identified from a broader cross-sectional study which was conducted to determine the prevalence of chronic periodontitis in 30–60 year old adults in Colombo district Sri Lanka. The study included 694 cases and 706 controls. Data were collected by means of a pre-tested interviewer administered questionnaire to obtain information about socio-demographic and behavioural factors, a physical examination to record anthropometric measurements and an oral examination.ResultsBeing a male, a Muslim, belonging to the 45–60 year old age group, having less than 12 years of education, using the finger to clean teeth, current smoking, current betel quid chewing, self-reported diabetes and hypertension emerged as risk factors for chronic periodontitis.ConclusionsSeveral socio-demographic and behavioural factors as well as co-morbid conditions emerged as independent risk factors for chronic periodontits in this population. The findings could be used for planning programmes to reduce the burden of chronic periodontits in Colombo district Sri Lanka.