Health effects of nanoparticles are attracting considerable and increasing concern of the public and government worldwide. Carbon nanotubes represent one of the fastest developing nanoparticle materials with production set to increase rapidly as a consequence of the useful properties of this material (Donaldson et al., 2006). The pulmonary toxicity of single-walled and multi-walled carbon nanotubes delivered at high doses and dose rates to the lower respiratory tract of rats and mice induced a high acute inflammatory response with granuloma formation and fibrosis as late effects (Warheit et al. 2004; Muller et al. 2005). However, the reports about toxicological research of multi-walled carbon nanotubes by the oral, dermal and ocular routes are not yet published. The oral, dermal and ocular routes represents an important portal of entries for MWCNT since several consumer which are on the market, already contain multi-walled carbon nanotubes. Few studies provided only scanty insights into the interaction of MWCNT with the human body after entering via different portals. Hydroxylated single-walled carbon nanotubes (SWCNT) administered by gavage in mice (100 μL of a 15 μg/mL solution) are distributed to most of the organs and tissues, except the brain (Wang et al., 2004). The study by Wang et al., (2004) shows in mice that the radiomarked hydroxylated singled-walled carbon nanotubes administered intraperitoneally (100 μL of a 15 μg/mL solution) are distributed throughout the body, except the brain, pass through several compartments and are retained in the bones. Monteiro-Riviere et al. (2005) found multi-walled carbon nanotubes (MWCNT) in the cytoplasmic vacuoles of human epidermal keratocytes in vitro (up to 3.6 μm long), a decrease in cell viability and a significant increase in an inflammation marker (interleukin8). This demonstrates the capability of MWCNT to penetrate the cell membrane. Huczko and Lange (2001) studied the effects on the skin and eyes of exposure to carbon nanotubes. The application of a saturated filter of a solution containing nanotubes did not cause irritation or allergy in volunteers. Ocular instillation of an aqueous suspension of nanotubes in rabbits did not cause irritation. In the light of the increased production and proposed use of MWCNT in consumer products, there is a need for screening the potential toxicity of these nanoparticles. In the present study, we have made an attempt to investigate the acute oral, dermal, acute dermal irritation, eye irritation and skin sensitization potential of two different sizes (140±30, 1015nm) of MWCNT.