The toxicity of smoke is often being studied using cigarette smoke condensate (CSC) samples. In this project, twelve chemical components of tobacco leaf, representing about 50% of its dry weight, were selected. They included carbohydrates, amino acids, proteins, polyphenols and carboxylic acids. They were individually combusted and the bioactivities of their combustion products (i.e. condensates) were assayed using three in vitro tests. The mutagenic potencies were assessed with the Bacterial Reverse Mutation / Ames test (Salmonella typhimurium TA98 and TA100). The induction of chromosomal damage was determined with the Micronucleus test (IVMNT), using V79 Hamster lung fibroblast cells. The Ames test and IVMNT were conducted both in the presence and absence of rat liver microsomal S9 fraction, to assess metabolites' toxicity. The Neutral Red Uptake cytotoxicity test (NRU) was also conducted using V79 cells. Ames data confirmed the mutagenic potencies of combustion condensates obtained from nitrogenous compounds (amino acids and proteins) of tobacco. The IVMNT showed that precursors of phenols in smoke (chlorogenic acid and lignin) exhibited significantly higher levels of toxicity compared to other tobacco components. While S9 activation amplified the Ames response to combustion products, it significantly inhibited the toxic response measured with the IVMNT. NRU data demonstrated the increasing cytotoxicity induced following longer exposure time to condensates from nitrogenous and phenolic components. These toxicological data characterize the toxicity of the combustion products of twelve tobacco constituents. They also underline different mechanisms of toxicity as revealed by the different bioassays' responses.