6 species of amphipods were studied for the detection of oxygen- and рН preferences, among them 5 Baikalian endemic species: Gmelinoides fasciatus (Stebb.), Eulimnogammarus cyaneus (Dyb.), E. verrucosus (Gerstf), E. vittatus (Dyb.), Brandtiaparasitica (Dyb.) and Palearctic Gammarus lacustris Sars. All investigated species possessed similar рН preferences which varied from neutral to alkalescent values of a hydrogen indicator. According to the decreasing level of oxygen-preferences the investigated species could be arranged in the following order: E. verrucosus = E. vittatus < E. cyaneus < G. fasciatus = G. lacustris. There was not an expressed reaction to the change of oxygen level in Baikalian B. parasitica; that probably testifies the full (or partial) reduction of the reaction in connection with their symbiotic way of life.