essential (volatile) oil from aerial parts of tamarix aphylla (l.) h.karst. (tamaricaceae) grown wild in jordan was hydrodistilled by clevenger apparatus and analyzed by means of gc and gc-ms techniques. in vitro screening of potential cytotoxicity of the aqueous (ae) and ethanol (ee) extracts was also evaluated against human breast adenocarcinoma (mcf-7), colorectal adenocarcinoma (caco-2), and pancreatic carcinoma (panc-1) cancer cell lines as well as normal human fibroblasts. gc-ms analysis of t. aphylla eo revealed its richness in nonterpenoid nonaromatic hydrocarbons (52.39%), with predominance of 6,10,14-trimethyl-2-pentadecanone as the principal component. biologically, the plant extracts exhibited cytotoxicity effects in dose-dependent manner against most of the tested cell lines, but potent effects were only predicted against mcf-7 cells with ic 50 values of 2.17 +/- 0.10 and 26.65 +/- 3.09 g/ml for t. aphylla ae and ee, respectively. t. aphylla ae demonstrated a comparable cytotoxic effect with that offered by the control drug cisplatin (ic 50 value of 1.17 +/- 0.13 g/ml), even with higher safety profile against normal fibroblast cells (ic 50 values of t. aphylla ae versus cisplatin: 79.99 +/- 4.90 versus 9.08 +/- 0.29 g/ml). t. aphylla extracts could be a valuable source for cytotoxic agents with high safety and selective cytotoxicity profiles. unfortunately, no antiproliferative potential against caco-2 or panc-1 cancer cell lines was detected at a concentration less than 30 g/ml.