This study examined the effects of separate and combined applications of 3-methylcholanthrene, a polycyclic aromatic hydrocarbon and potent carcinogenic agent, and butylated hydroxytoluene, the antioxidant food additive, on the glycogen levels of liver, muscle, testis, and tumor tissues in rats. Adult male Wistar albino rats weighing 100-110 g at 8 weeks of age were used in this study. This study consisted of a control group (n = 9) and 3 different experiment groups in which rats were chronically treated with 3-methylcholanthrene (n = 9) or butylated hydroxytoluene (n = 11) or a combination of these agents (n = 14). Rats were intraperitoneally injected with a 200 mg kg(-1) dose of butylated hydroxytoluene and a 40 mg kg-1 dose of 3-methylcholanthrene. At the end of the 26-week experimental period, tissues of rats killed via cervical dislocation were placed in 10% trichloroacetic acid for glycogen determination. Our results showed that the administration of 3-methylcholanthrene, butylated hydroxytoluene, and 3-methylcholanthrene + butylated hydroxytoluene caused statistically significant changes in the glycogen levels of liver, muscle, and testis tissues, and glycogen was stored in tumor tissue.