We studied the carbon monoxide (CO) fractions in hookah and cigarette smoke, using a carbon monoxide micro smokerlyzer (model EC50, BEDFONT, U.K.). Mean carbon monoxide fractions (% by volume) of hookah smoke, using domestic charcoal were 0.38 +/- 0.07 (large hookah; unfiltered); 1.40 +/- 0.43 (small hookah; unfiltered); 0.34 +/- 0.06 (large hookah; filtered); 1.36 +/- 0.35 (small hookah; filtered) and 0.41 +/- 0.08 (cigarette smoke). The highest fractions were obtained with small size hookah and increase in size of hookah (i.e., volume of air in water base, fire bowl volume, pipe length, etc.) reduced the CO fraction significantly (P < 0.001). The fractions of cigarette lie between large and small hookah. The fractions vary slightly with different varieties of tobacco, e.g., CO fractions with Dera wala tobacco are significantly low (P < 0.05). Use of commercial charcoal gives significant rise in CO fractions (P < 0.001). Comparison of filtered and unfiltered smoke shows no significant difference in values. We conclude that the CO hazard is as high with hookah smoking as with cigarette smoking.