We surveyed Caucasian black grouse Tetrao mlokosiewiczi residing on the Lagonakskiy Ridge, northwestern Caucasus, Russia, in June-July 1998, and on the Magisho Ridge in July 1999. Weather affected habitat use by brood hens: on sunny days 18 broods were encountered in meadows, six in ravines, and three in pine forests; on wet days broods moved to the ridge tops (N = 9) and only one was observed in pine forest. Subadult males used the same habitats as females with broods. Seven of eight adult males were encountered in ravines; only one was encountered in a meadow. Habitat use by adult males was not affected by weather and differed from habitat use by females and subadult males. Well-camouflaged females, chicks and subadult males used relatively open, food-rich habitats, whereas black adult males preferred ravines, where nutrition was poor, but where tall grass protected them from aerial predators. One nest with five hatched eggs was found. In broods an average of one chick per 10 days was lost. A goshawk Accipiter gentilis killed one adult female. Our density estimate of 2.3 adults/km² for the Lagonakskiy Ridge was similar to densities reported elsewhere (2.3 ± 1.2; N = 7).