This term refers to prolonged, unexplained crying in 1-3 month-old infants. It is poorly defined and may be used to refer to amounts of crying, to the inference that the crying is caused by gastrointestinal pain, or to the reports of parents that the crying is a problem. Here, it is used broadly to refer to prolonged bouts of crying that occur without apparent reason in 1-3 month-old infants, together with parental concern about the crying.