With an annual global production of approximately 25 million tons, the common bean (Phaseolus vulgaris L), a member of the genus Phaseolus, is one of the major protein sources used as food for humans. In this study, it was aimed to investigate the genome size of the common bean genetic resource collection (154 common bean accessions) in Turkey by flow cytometry (FCM) and determine whether geographical variables affected the genome size. In addition, the number and distribution of 5S and 45S ribosomal DNA loci were designated by performing a fluorescence in situ hybridization (FISH) analysis in some of the accessions. The FCM analyses revealed that the mean nuclear DNA content of the accessions varied from 1.28 pg2C-1 to 1.55 pg2G1 (mean 1.35 pg2C-1), and the differences between these accessions were statistically significant (P < 0.01). Intraspecific variation in the genome size was determined, and a positive correlation was found between the altitude and genome size. However, latitude and longitude did not have any statistically significant effect on the genome size. In the principal coordinate analysis, the accessions were divided into 3groups. Based on the results of the FISH analysis performed on 5 different accessions with varying genome sizes, using 5S and 45S rDNA genes as probes, the number of 5S rDNA loci was 4 in the common bean and stable among the common bean accessions, while the number of 45S rDNA loci was highly polymorphic, varying between 6 and 16. Consequently, it was determined in the present study that the genetic resource collection of common bean had a wide variation in terms of genome size and genome organization.