For the first time, quantitative data was obtained on plasma treatment of living mammalian cells. The nonthermal atmospheric discharge produced by the plasma needle was used for treatment of mammalian endothelial and smooth muscle cells. The influence of several experimental parameters on cell detachment and necrosis was tested using cell viability assays. Interruption of cell adhesion (detachment) was the most important cell reaction to plasma treatment. Treatment times of 10 s were enough to detach cells in the cultured cell sheet. Under extreme conditions, cell necrosis occurred. Cell detachment without necrosis could be achieved at low voltages. It was shown that the thickness of the liquid layer covering the cells was the most important factor, which had more influence than treatment time or applied voltage. The results show no remarkable differences between the responses of the two cell types.