Introduction: Single wall carbon nanotubes(SWCNT) represent a material of high interest, recently, due to many biomedical application that have been imagined. Recent in vitro studies have demonstrated increased oxygen free radical production after cells exposure to carbon nanotubes. However, exposure effects on mesenchimal stem cells and the implication of oxidative stress mechanisms in SWCNT toxicity is still unclear. Material and method: High purity carbon nanotubes were functionalized with single strand DNA through sonication(7 hrs). Consecutive dilutions were made to obtain 1, 5, 10 and 20 mg/l concentrated solutions. Separate samples of amniotic membrane stem cell line were exposed to the above mentioned solutions. For each concentration a control sample was assigned. MTT assay was performed to assess proliferation. For 10, and 20mg/l SWCNT concentration 5-(and-6)-carboxy-2',7'- dichlorofluorescein diacetate (DCFDA) assay was performed. Evaluation was performed at baseline, 24 and 48 hrs interval. Baseline proliferation values were considered as 100%. Dynamic proliferation curves were constructed and differences between curves were tested using non-parametric methods. Results: Stimulation of proliferation was detected for low concentrations (1mg/L, 5mg/L), while high concentrations (10mg/l, 20mg/l) induced decrease of proliferation rate. All effects were transitory. Proliferation effects were dose- dependant, with significance obtained between 10mg/l and 20mg/l and low concentrations (1mg/l and 5mg/l), respectively (p<0.05). High concentrations of SWCNT induced high levels of fluorescent signals at 24 and 48 hours, respectively, with peak values at 24 hours (p<0.05). Conclusions: Different concentrations of CNT induce different proliferation results. Inhibitory proliferation effects are induced by high dose of exposure and invove oxidative stress mechanisms. Antioxidant supplementation may be necessary for drug- vehicle applications of SWCNT. Founded by National Grant Contracts:PNCDI-42-121- NANOCITOX, PNCDI-42-111-VACSTEM, PNCDI-41- 077/2007-PLACSTEM