Routes, methods and key results of two mammalian expeditions undertaken by German and Mongolian zoologists in 1995 and 2002 are described. The 1995 expedition trapped a sample of Mongolian gerbils (Meriones unguiculatus) (n = 167) with high genetic diversity for further breeding of a new wild gerbil strain in Germany. The 2002 expedition collected 265 mammals from 23 species during an extended west-eastern survey from 96°to 113°E along the transient zone of the semi-desert to the Gobi desert near 44°to 45°N. Methods applied included dissections, behavioural experiments, vocalization recording, determination of dominant plants and livestock. New techniques were introduced to record surface activity of small mammals. Most mammals trapped in the steppe were Mongolian gerbils with an estimated density of 2400 -6600 individuals per km 2 . The highest diversity was found in the desert and semi-desert region and included Hemiechinus auritus, Meriones unguiculatus, Salpingotus crassicauda, Pygeretmus pumilio and Cardiocranius paradoxus, which were restricted to southern Mongolia. The need for further complex expeditions through the arid zones of Mongolia are discussed.