Mass chain yield distribution has been done in the thermal neutron–induced fission of 239Pu by measuring the cumulative yields of various fission products within the mass range of 78 to 159 and the independent yields of a few products. An off-line gamma-ray spectrometric technique was used to measure the gamma-ray activities of the fission products. From the measured values of the cumulative yields, the post-neutron mass chain yield distribution was obtained after applying the charge distribution correction. Data from the present and earlier work of our laboratory in the 239Pu(nth,f) reaction were compared with similar data of 238,241Pu(nth,f) and 240Pu(n,f) reactions, and it was found that the fine structures of the mass yield distributions are similar. The mass yield distribution in the 239Pu(nth,f) reaction was also compared with those of 229Th(nth,f) and 252Cf(SF) reactions to examine the effect of charge and mass difference of the fissioning systems on the mass yield distribution. It was found that the asymmetric standard I mode of fission is favorable in the 238,239,241Pu(nth,f) and 240Pu(n,f) reactions whereas the standard II mode is favorable in the 229Th(nth,f) and 252Cf(SF) reactions.