Four specimens of Ocimum viz. O. basilicum L., O. gratissimum L. and two forms of O. tenuiflorum L. (Green form and Purple form) were cytogenetically studied for authentic characterization. The green and purple forms of O. tenuiflorum L. are found to possess 2n=36 and 2n=34 chromosomes, respectively. On the other hand, 2n=54 chromosomes were observed in O. basilicum L. and 2n=40 chromosomes in O. gratissimum L. In this study, 2n chromosome number of O. tenuiflorum L. (Purple form) and O. basilicum L. are the first report. Six sub-metacentric chromosomes were observed in the green form of O. tenuiflorum L. (30m+6sm) while other three specimens possessed only metacentric chromosomes. These four specimens of Ocimum L. have distinct CMA- and DAPI-banding patterns based on the number, location, intensity and percentage of GC- and AT-rich repeats. Two CMA fluoresced satellites were observed in only O. gratissimum L. indicating stain specific nature of the satellite portions. Moreover, it was possible to identify certain marker chromosomes specific for each specimen with the help of CMA and DAPI banding pattern. The two forms (Green and Purple) of O. tenuiflorum L. are sharply different in respect of conventional karyotype and fluorescent banding pattern. Thus, a subtle revision is essential regarding their taxonomic status.