Abstract: A diaper for animals includes an inner permeable sheet, an outer water-proof sheet, an absorbent material located between the permeable sheet and the water-proof sheet and a tail area defined by a line of weakness in the water-proof sheet. The tail area is located at a place on the diaper that corresponds to the location of an animal's tail when the diaper is worn by an animal. A hole may be manually formed in the water-proof sheet for accommodating the tail of an animal by manually separating the water-proof sheet along the line of weakness.