Many health care professionals believe that there is a very short interval between an act of ultimately lethal infant shaking and the onset of symptoms (altered consciousness, convulsions, respiratory distress, and so on). We reviewed the English-language medical literature on the shaken baby syndrome for case reports or other information that documents the time of onset of symptoms after an act of ultimately lethal infant shaking. The medical literature contains minimal data that substantiate or contradict the contention that is stated here.