Catechol and alkylcatechols are known co-carcinogens present in cigarette smoke. Hydroquinone, although nongenotoxic, can form a metabolite with nephrotoxic properties and is a potential human carcinogen. The formation of dihydroxybenzenes during smoking originates with the pyrolysis of several precursors from tobacco. These include cellulose, chlorogenic acid, rutin, etc. The present study attempts to quantitate the contribution of chlorogenic acid and rutin to the formation of dihydroxybenzenes and of some alkyldihydroxybenzenes. Also it estimates the contribution to the formation of dihydroxybenzenes from other potential precursors including glucose, fructose, sucrose, cellulose, pectin, starch, and lignin. The study was done in three parts: 1. pyrolytic evaluation of the amount of dihydroxybenzenes in smoke generated from isolated potential precursors; 2. analysis of smoke from cigarettes made from a variety of tobaccos (14 single grades) and two blended cigarettes, followed by correlations of dihydroxybenzenes yield with the tobacco content of various suspected precursors; 3. addition of chlorogenic acid or rutin to several tobaccos followed by the smoking of the spiked cigarettes and measurement of dihydroxybenzenes yield increase. The study shows that for a variety of singlegrade cigarettes and for two blended cigarettes (one being the 2R4F Kentucky reference), the contribution of chlorogenic acid and of rutin to the formation of catechol and hydroquinone in smoke depends on the blend. For the 2R4F cigarette, the contribution from chlorogenic acid is 8.7% for catechol, and 7.7% for hydroquinone (for ISO smoking protocol). For the same cigarette, the contribution from rutin is 3.7% for catechol and 5.1% for hydroquinone. The results of the study are in agreement with a previously reported finding indicating that chlorogenic acid contributes about 13% to the catechol formation in smoke for the 1R1 Kentucky reference cigarette. The study results suggest that other components in tobacco, besides chlorogenic acid, rutin, glucose, fructose, sucrose, cellulose, pectin, starch, and lignin are major contributors to the formation of catechol and hydroquinone in cigarette smoke.