Objective. To determine the prevalence, risk factors, characteristics, and treatment practices of known adult hypertensives in Saudi Arabia. Methods. Cross-sectional community-based study using the WHO stepwise approach. Saudi adults were randomly chosen from Primary Health Care Centers catchment areas. Data was collected using a questionnaire which included sociodemographic data, history of hypertension, risk factors, treatment practices, biochemical and anthropometric measurements. Collected data was cheeked, computer fed, and analysed using SPSS V17. Results. Out of 4719 subjects (99.2% response), 542 (11.5%) subjects were known hypertensives or detected by health workers in the past 12 months. Hypertension was significantly associated with age, gender, geographical location, education, employment, diabetes, physical inactivity, excess body weight, and ever smoking. Multiple logistic analysis controlling for age showed that significant predictors of hypertension were diabetes mellitus, ever smoking, obesity, and hypercholesteremia. Several treatment modalities and practices were significantly associated with gender, age, education, and occupation. About 74% were under prescribed treatment by physicians, 62% on dietary modification, 37% attempted weight reduction, 27% performed physical exercise, and less than 7% used herbs, consulted traditional healers or quitted smoking. Income was not significantly associated with any treatment modality or patient practices. Conclusion. Hypertension (known and undetected) is a major chronic health problem among adults in Saudi Arabia. Many patients' practices need changes. A comprehensive approach is needed to prevent, early detect, and control the disease targeting, the risk factors, and predictors identified.