A small animal litter box which comprises an upper tray with a perforated bottom wall for carrying litter material, and a lower tray for receiving urine and particles dropping from the first tray through the perforated bottom wall thereof. The first tray contains litter material in the form of pellets that are disintegrated into smaller particles when the pellets absorb urine, and the perforated bottom wall has holes dimensioned such that smaller particles from disintegrated pellets pass through the holes while intact pellets are prevented from passing through the holes.