This paper aims to investigate the differences between the low-temperature oxidation behavior of some Turkish coals having different ranks by statistically analyzing the formation rates of CO2 and CO as well as the ratio of CO/CO2. In order to do this, oxidation experiments were performed on four Turkish coals grouped at -425+212, -212+150, and -150+106 mu m size groups and oxidized at 40, 60, and 90 degrees C, respectively. Then, a step-by-step multiple-regression analysis was conducted to assess the effect of rank, temperature, and particle size by determining the variation in the formation rates of CO and CO2 as well as the ratio of CO/CO2 over time for the data set obtained from the experiments. Regression results showed that as the rank increases the formation rates of CO and CO2 it also increases the magnitude, and they decrease faster over time. The effect of temperature was clearly confirmed by the regression results as indicated by the temperature dummy, whereas the effect of particle size at close ranges of size groups was not clearly acquired.