Nineteen methanolic crude plant extracts of Labiatae family, collected in Greece from different locations, were evaluated for cytotoxic activity against brine shrimps and three human cancer cell lines along with a normal mouse cells as a control cell line. In the brine shrimp lethality test, Mentha pulegium was the only sample found to be active with an LC(50) value 347.3 micro g/ml, while all remaining samples had LC(50) values greater than 1000 micro g/ml. In case of Caco-2 and HepG2 cell lines, only one sample, namely Thymus parnassicus Halacsy, was active with LC(50) values 44.6 and 50.3 micro g/ml respectively, while against MCF-7 cell line, two samples, namely, Clinopodium vulgare L. (LC(50): 60.4 micro g/ml), and Thymus parnassicus Halacsy (LC(50): 54.7 micro g/ml), were found active.