The aim of this paper is to study relationship between bi-ological activity of a group of 140 gemini-imidazolium chlorides and three types of parameters: structure, surface active, and molecular ones. Dominance-based rough set approach is applied to obtain decision rules, which describe dependencies between analyzed parameters and allow to create a model of chemical structure with best biological activity. More-over, presented study allowed to identify attributes relevant with respect to high antimicrobial activity of compounds. Finally, we have shown that decision rules that involve only structure and surface active attributes are sufficient to plan effective synthesis pathways of active molecules.