This is a survey of the genetics of microphthalmos and the heritable syndromes in which microphthalmos occurs. New syndromes are delineated such as the autosomal dominant anophthalmos-microphthalmos-coloboma syndrome, the autosomal dominant microphthalmos, microcephaly, lacunar retinal atrophy syndrome, the autosomal recessive anophthalmos-microphthalmos-coloboma syndrome, the autosomal recessive syndrome with anophthalmos or microphthalmos and genital malformations, and the autosomal recessive syndrome with microphthalmos, microcephaly and retinal falciform folds. Nanophthalmos is described as a poorly defined phenotype and rejected as a genotype. Several other genetic entities with microphthalmos are reviewed and recent descriptions are surveyed.