Pinworm infection is a very common diagnosis in young children that is not always confirmed through laboratory evaluation before empiric therapy is prescribed. This article describes a toddler who was treated several times for pinworms because small white worms were seen in her perianal area. Laboratory analysis of parasite material found in her diaper later confirmed a diagnosis of dipylidiasis. Because the signs of dipylidiasis and pinworm infection overlap and the treatments for these parasitic infections are different, the laboratory should clinically confirm suspected persistent or recurrent pinworms.