Analysis of 230 published cases of the EEC syndrome revealed that, besides the cardinal symptoms (ectrodactyly, ectodermal dysplasia and clefting), lacrimal tract abnormalities and urogenital abnormalities are part of this syndrome. Mental retardation and various abnormalities and dysmorphisms of the ears and face, reported in EEC syndrome, do not really seem to be part of it. Conductive hearing loss is associated with clefting. A score for the severity of symptoms in the EEC syndrome is described, and using this score it appears that isolated cases are generally more severely affected than familial cases. We did not find signs of genomic imprinting or anticipation in published EEC families. We did find, however, that interfamilial variability is significantly larger than intrafamilial variability, pointing to genetic (allelic?) heterogeneity. The penetrance of the EEC-mutation is estimated to be between 93% and 98%.