Unusually prominent lateral palatine ridges have been found to be a nonspecific feature of a variety of disorders in which there is either neuromotor dysfunction or a malformation which prevents tongue thrust into the palatal vault. Observations of the lateral palatine ridges in 3 fetal specimens and in 260 normal individuals over a wide range of ages revealed that these structures are normally more prominent during prenatal life and infancy. With increasing age these ridges normally become progressively flattened and usually disappear by age 5 years. The observation of unusual prominence of these ridges in infants with neuromuscular dysfunction as well as in those with malformations which limit tongue thrust into the palatal vault suggests that a long-standing deficit of tongue thrust is the common pathogenetic mechanism. Prominent lateral palatine ridges may be misinterpreted as a true "narrow, high-arched palate", which is a much less common anomaly. This distinction is important clinically, since prominent lateral palatine ridges most commonly imply a long-term deficit of neuromuscular function and thus may be an important diagnostic clue to alterations dating back to early prenatal development.