Prevalence, sociodemographic patterns and medical co-morbidity of smoking among a cross-section of primary health care (PHC) clients in Saudi Arabia were examined. We used a 44-item semistructured questionnaire to collect data from 1752 patients at 25 randomly selected PHC centres. Percentage of smoking was 52.3%. Although 85% were adult smokers, 8.6% began smoking before age 12. Smokers gave overlapping reasons to smoke including peer pressure; non-smokers gave religious and health logics against smoking. Of all smokers, 92.8% wanted to learn cessation strategies, 11.8% were ignorant of hazards and 32.4% reported manifestations of nicotine withdrawal. Besides alcohol use (13.4%), 81.8% had co-morbid physical disease.