Megalocornea (corneal diameter > or = 13 mm) is associated with mental and neurological impairment, and minor anomalies in Neuhäuser syndrome (megalocornea-mental retardation syndrome). Here we report 4 new cases of megalocornea and mental retardation. Those unrelated patients have a consistent pattern of anomalies with possible recessive inheritance which clearly differs from that of the original patients of Neuhäuser et al. [1975]. We discuss the heterogeneity of the syndromes with megalocornea and mental retardation. Based on these cases and on a review of the literature, we suggest a provisional clinically oriented classification in 5 subtypes: (1) a recessive form type Neuhäuser (with iris hypoplasia and minor anomalies), (2) a recessive form type Frank-Temtamy (with camptodactyly, scoliosis and growth retardation), (3) a recessive type 3, including our 4 personal cases (with normal irides, severe hypotonia, relative or absolute macrocephaly and minor anomalies), (4) a possible Frydman type (with normal irides, megalencephaly and obesity), and (5) provisionally unclassifiable cases.