Salvia officinalis is known to be cytotoxic and cytostatic and is potentially useful as an anticancer and antimicrobial agent. Ciprofloxacin and metronidazole besides Salvia have been applied clinically and proved to be of a great benefit as antimicrobial agents in medicine. Ciprofloxacin and metronidazole are used because of their known effect on DNA replication directly or indirectly. This study was aimed to evaluate the effects of aqueous solutions of Salvia officinalis, ciprofloxacin and metronidazole on the pectrophotometric properties of DNA isolated from leukemic and healthy human peripheral lymphocytes, DNA of E.coli and calf thymus double-stranded DNA. The design of this work was studied in vitro for the isolation and purification of DNA and monitored spectrophotometrically by 260nm/280nm ratio. The ratio of absorbance at 260/280 was between "1.8-2" which indicates that the isolated DNA is pure. When DNA was exposed to different concentrations of an aqueous solution of Salvia officinalis, ciprofloxacin and metronidazole, DNA changes were noticed by absorbance at 260nm before and after exposure.