Karyotypic analysis of sixteen cultivars of Phaseolus acutifolius A. Gray showed reasonable differences between the cultivars on chromosome length, position of primary constriction and in TF%. Only in two cultivars, a pair of chromosomes was secondarily constricted and most of the chomosomes in all the cultivars, excepting the Nebraska cultivar, possess mostly medianly constricted chromosomes. In Nebraska cultivar, there are 4 pairs of secondary constricted chromosomes and most of the chromosomes possess submedian primary constrictions. An average karyotype of Phaseolus acutifolius has been suggested basing in the results included herewith.
The observation of TF% ranging from 34.50 to 38.79 revealed a symmetrical karyotypes for 10 cultivars. The others 6 cultivars were observed to be asymmetrical with TF ranging from 30.45 to 33.74. The importance of karyotypic differences in evolution of varieties within a species has been discussed.