Abstract: In Russia, traditions of track observations and the use of tracking techniques in studying the ecology and behavior of mammals were founded by A.N. Formozov. An analytic review of his data on large carnivorous mammals (tiger, snow leopard, wolf, brown bear, wolverine, and others) is given. A special detailed observation of animals' tracks as a source of information on their life is shown only to start. The efficiency of track observations in various fields of studies, including counting animals, is estimated. The values of day and night distances for various animal species, given in literature, have never been properly substantiated methodically. The tracking method is the most effective in studying the use of the home range by animals, drawing the network of their movements and scent-marking behavior. The hunting behavior of large predators in dense forests is can only be deduced by observing their tracks. In some cases, the use of tracking has a distinct advantage over radio tracking. The main propositions are illustrated by the materials of the author obtained in various Russian regions (in forests of the northern Russian Plain and southern Far east) for 1958-1998.