The research period started from April 2002 to February 2004 and continued several axles. The aim of the present study is to investigate the anti-micobial, anti-tumor, cytogenetic and cytotoxic effects of three Iraqi medicinal plants extracts. The plants used were dried leaves (Cucurbita maxima, Cucurbita pepo), dried roots of (Z in giber OFFECINALE) and dried seeds of (Peganum harmala}. The plants extracts have inhibitory effect on cancer cell lines (HEP, RD) and some points were investigated as following:- l-The plants extracts have a good anti-bacterial activity against the gram positive and gram negative bacteria which including E.coli. aureusus.and P aurogenosa in different concentrations (0.5,1,5,10) mg/ml. 2-The toxicity of the plant extracts was determined in human peripheral lymphocyte using four concentrations of the extracts (I, 10, 100. 1000 ug/ml for three days. Short-term assay (MTT) was employed. There was no toxic effect of the plants extracts on human lymphocyte cells. 3-Some ]Dlants extracts which were extracted by (hexane, chloroform- methanol) from Cucurbita maxima, Cucurbita pepo. Zingiber offecinale and Peganum harmala and the inhibitory effects of six different concentrations (0.1,1,10,100,1000,10.000) ug/ml was 4-'The hexane, chloroform, and methanol extracts of (Cucurbita maxima,Cucubita pepo,, Zingiber offecinale (100,250,500) (ug/ml and Pegamum harmala there ideal concentrations (25, 50,100)ug/mll, showed an innhibitory effect of spontaneous chromosomal aberrations and sister chromatid exchanges formation in the peripheral blood lymphocyte cells.5-The results showed that the ideal concentrations of different plants extracts have a good protective activity. Increasing the mitotc. ,) index, replactive index and cell cycle progression activity depicted this. -6-The results showed that the mutagenic effect of the anticancer drug (MTX) was increased as the concentration was gradually increased Therefore, the concentrations (50, 25, and 10) ug/ml respectively was used in the experiments. The optimal time for effect of the drug was hours. The toxic and mutagenic effects of the drug included mitotic index, replactive index and the cell cycle progression on peripheral blood lymphocyte cells, increasing the chromosomal aberrations and sister chromatid exchanges.