Objective: Determination of growth characteristics of different cell types is considered as an important way to study the effect of extracellular molecules such as different culture medias in vitro. A normal growth curve consists of three phases: 1-the lag phase is the time after subculture and reseeding in which cells adapt with new conditions, 2-the log phase is the period of exponential increase in cell number and 3-the plateau phase in which cell growth is reduced due to contact inhibition and depletion of nutrients. In this study we analyzed these parameters for mesenchymal stem cells. These data will be helpful for researchers who want to study effect of different culture medias and serums efficacy. Materials and Methods: Mesenchymal stem cells were harvested from a culture plate, counted and brought into suspensions of 1×105 cells /ml (concentration A), 3×104cells/ml (concentration B) and 1×104 cells/ml (concentration C), in 25 ml of media for each concentration. One milliliter (ml) of each was seeded in an arrow of two 24 well plates. Plates were incubated at 37°C in a humid atmosphere with 5% CO2. Media exchange was done every three days. Every day one well of each concentration was trypsinized and cells were counted with a hemocytometer. Finally growth curve was drawn and parameters were calculated. Results: Lag time was determined as more than one day, 4 days and 4 days, with log durations of 3 days, 4 days and 4 days for concentrations A and B and C respectively. Population doubling time was calculated by the formula "(log(N1)- log(N0))/log2" and results were 1.6 , 1.12 and 1.53 for concentrations A, B and C. Conclusion: Growth curve contained all three phases indicating that higher seeded cell number results in a lesser lag time and also a lower log duration, but lower cell concentrations lead to higher rates of proliferation. These data will be useful in understanding the effect of different culture medias, various growth factors and drugs on the growth characteristics of mesenchymal stem cells.