The 2C and 4C nuclear DNA amounts were estimated in eight diploid species, belonging to three diverse genera (Vicia, Tephrosia, and Phlox) and their corresponding colchitetraploids. In P. drummondii, T. purpurea, and 7: oxygona tetraploids the deviation from the expectation was highly significant. The DNA in f? drummondii was further discarded in subsequent (C,, C,) generations, thus attaining an overall reduction of about 25%. The DNA content in the subsequent generations was the same as that of C,. It is concluded that rapid DNA loss in the first and subsequent generations was not only associated with the substantial increase (30-66%) in the seed set, but it also helped in the establishment and stabilization of the tetraploid. The possible relationship between such a nucleotypic change and success of polyploids is discussed. The DNA change from the expected value in the f? drummondii tetraploid was achieved by equal decrement to each chromosome independent of size, i.e., small chromosomes loose the same amount of DNA as the large chromosomes.