G,Q and R-binding pattern comparisons between the Murrah type of Bubalus bubalis L. (2n - 50) and the Holstein Friesian breed of Bos taurus L. (2n = 60) chromosomes revealed that the autosomes are similar in both species; in the former, the five pairs of submetacentrics correspond to centric fusions of chromosomes 1-29, 2-22, 8-19, 5-28 and 16-25 in the latter. Silver staining on somatic cells of buffalo revealed telomeric AG-NORs located on six pairs of autosomes, identified as 3p, 4p, 8, 21, 23 and 24. Only one pair of nucleolus organizer chromosomes is common to both species, namely the 4p of buffalo which corresponds to the 28 of cattle. The remaining NORs are located on different pairs. Out of 18 individuals, the number of Ag-NORs per cell varied between 3 and 10, with a mean value of 6.3 +/- 1.7; the mean number of nucleolar associations per cell was between 0.1 and 1.8. In the total population of 317 cells the two variables followed the binomial and the Poisson distributions, respectively, and their correlation coefficient was not statistically significant (r = +0.36). In addition to the mean number of Ag-NORs, the mean number of nucleolar associations per cell should be used for a better understanding of the differences among individuals.