Background: Various MTT assay methods are proposed to obtain the cell sur- vival parameters.Objective: Determining the survival curve characteristics of two cancerous cells of interest based on a common and a novel MTT assay method after exposing them to ionizing radiation.Method: A common and a novel MTT assay method were used and compared for obtaining the F10B16 melanoma and 4T1 breast adenocarcinoma survivals after exposing them to ionizing radiation from a Co-60 machine. To obtain the survival parameters of the cells based on the common method, the cells were inoculated in 96-well plates. After irradiating the plates, the MTT assay was performed over the following days for a period of 8 days. Thereafter, the survival fraction was calcu- lated from a simple equation for every day from which the best day was selected. To acquire the cellsâ€™ survival parameters based on the novel method, extensive experi- ments were performed on a large number of samples. Then, the MTT assay was done in every day following various experimental treatments to acquire the exponential growth. Finally, the cellsâ€™ survivals were determined by measuring the space between relevant growing curves.Results: At low doses (<4Gy) the two MTT assay methods indicated the same re- sults. However, at higher doses there were significant differences among the findings.Conclusion: Both of the MTT methods indicated that the cellsâ€™ responses are de- pendent on the dose levels used. Although the implementation of the common MTT assay method is simpler, the novel method seems to show more precise and reliable results at all levels of radiation doses.