The distribution of asteroids with diameters greater than 130 km is analyzed using a maximum likelihood method. The mass distribution index of these asteroids for various diameter ranges, taxonomic classes, and distance zones is estimated together with the large sample errors and confidence intervals. This method suffers none of the major defects of the least squares linear regression method used by previous authors. It was found that the C- and S-type asteroids had very similar mass distribution indices. The distance zones I and IV have also similar indices as to the zones II and III, though the differences between zones are not statistically significant. It is found that all the asteroids in the range of diameter greater than 130 km can adequately be fitted by one mass distribution function of index 2.018 + or - 0.091. It is suggested that collisional fragmentation is the most likely process to have produced this distribution.