A single carboxyhaemoglobin (COHb) estimation of late evening blood sample among non-smokers, cigarette smokers, and sheesha smokers was evaluated among Saudis. The COHb level in smokers of 15 to 40 cigarettes a day ranged between 0.7 and 10.3 with a mean value of 6.1 +/- 2.58 COHb. Values among sheesha smokers ranged between 6.5 and 13.9 with a mean value of 8.8 +/- 1.83, significantly higher than those of cigarette smokers (P less than 0.001) for a given degree of exposure to tobacco smoke.