The synthesis and biological activity of a hitherto unknown class of compounds, the imidazolylthiazolidin-4-ones, are described. A two-step procedure has been elaborated starting from our previously described 2-aminoimidazoles. The application of microwave irradiation has been proven to be beneficial for the condensation of the imine with mercaptoacetic acid leading to the formation of imidazolylthiazolidin-4-ones. None of the compounds showed antiviral activity at subtoxic concentrations. Several compounds displayed a moderate cytostatic activity. These data form the basis for further improvement of the potential antiproliferative activity of this class of compounds.