We describe one type of the heterogeneous ichthyosis congenita group, inherited autosomal-recessively, noting its clinical and ultrastructural features based on the findings in a female patient, aged 30 at the time of first clinical and ultrastructural investigation, and supplemented with those of eight further patients, aged 2 to 22 years. Clinically this keratinization disorder was characterized by a generalized congenital ichthyosis with a reticulate skin pattern pronounced in a variable degree of severity, also involving the large flexures and the face, palms, and soles. Typical ultrastructural criteria were membrane structures, abnormal vesicular keratinosomes, vesicular complexes, and membrane-bound vacuoles within the cytoplasm of the granular cells, partly retained in the horny layer. A successful therapy with retinoids resulted in a complete removal of the hyperkeratoses but left the striking skin pattern unchanged. The morphological peculiarities remained unaltered as well. They are independent of the localization of the biopsies, of age and sex of the patients, and of oral and local treatment. Based on the clinical and ultrastructural features, this scaling disorder can be delineated against all other inherited ichthyoses and was termed ichthyosis congenita type III. A new nomenclature contributing to a distinct classification within the heterogeneous ichthyosis congenita group is discussed.