Cleft sternum is a rare malformation due to partial or total failure of sternal fusion at an early stage of embryonic development. Sternal clefts can be classified as superior, inferior, or complete. Here we report on a 2-year-old boy with inferior sternal cleft and complex cardiac malformation. We review a series of 9 children with sternal clefts, referred to us over a 10-year period. Hypothetical mechanisms for this developmental anomaly are discussed.