Craniofacial birth defects are the fourth most common congenital anomaly in newborns. Cleft lip and palate together represent the most common congenital deformity of the head and the neck. Oral clefts, including cleft lip (CL), cleft palate (CP), and cleft lip and palate (CLP) constitute a heterogeneous group of non-fatal birth defects known to be multifactorial in origin, in that both genes and environmental factors contribute to their aetiology. Due to both epidemiological and embryological similarities, CL and CLP are usually grouped together as cleft lip with or without cleft palate (CL/P). We will discuss their developmental pathogenesis, epidemiology and causes.