Forty-two species and 4 varieties belonging to 21 genera were collected from 40 tobacco samples on glucose- and cellulose-Czapek's agar at 28 degrees C and 45 degrees C. The most common mesophiles (at 28 degrees C) in tobacco on the two types of media were: Aspergillus flavus, A. flavus var. columnaris, A. fumigatus, A. niger, Penicillium chrysogenum and P. funiculosum. Two samples were heavily contaminated with members of Fusarium (F. moniliforme, F. oxysporum, F. solani). Some fungi were encountered only on plates of cellulose agar as Chaetomium globosum, Stachybotrys atra var. microspora and S. chartarum. At 45 degrees C the most prevalent fungus was A. fumigatus. Truely thermophiles were also collected: Humicola grisea var. thermoidae, Rhizomucor pusillus and Thermoascus aurantiacus. Based on biological assays (brine shrimp larvae (Artemia salina L.) and Bacillus megatherium test) and chemical analysis of chloroform extraction of tobacco (TLC and UV spectrophotometric), four samples (out of 40) had toxicity and four compounds of mycotoxins were detected namely; aflatoxins B1 & B2 (2 samples; 15.5 and 20.7 micrograms/kg), zearalenone (1 sample, 5.5 micrograms) and T-2 toxin (1 sample, 2.8 micrograms). For studying the tracing of aflatoxins in smoking cigarettes, three doses (10, 20 and 50 micrograms) of aflatoxins B1 and B2 (w/w, 1:1) were injected each in ten cigarettes. All extracts of cigarettes smoke proved to be non-toxic and mycotoxins not detected. However, aflatoxins were detected in topping filter (2.8, 3.5 and 8.8 micrograms/the three doses, respectively).