Two siblings with interstitial deletion of chromosome 14 not associated with ring formation were reported. Clinical features of the patients included failure to thrive, severe mental retardation, microcephaly, round face, hypertelorism, micrognathia and high-arched palate. They were common also in five previously reported cases. Other peculiar finding was hyperthyrotropinemia in their neonatal periods; mild hypothyroidism was found in the elder sister, and hyperthyrotropinemia was only transient in the younger sister. By a high-resolution G-banding analysis, the maternal origin of the chromosome with the deletion was noted.