All genera have thick fur, that of the montane genera, Lagidium and Chinchilla, being finer than that of Lagostomus, which occurs on the pampas. The pelage is coarser on the tail than on the body. The palms and soles of most forms are naked.
Coloration varies considerably among the genera.
The body form is slender. The forelimbs are relatively short, but the hind limbs are long and muscular. The forefoot has four long, flexible digits. The hind foot is elongate. Lagidium and Chinchilla have four digits on the hind foot, with relatively weak claws.