Aplasia cutis congenita (ACC) is a rare, congenital disorder characterized by localised or widespread absence of skin at birth with heterogeneous clinical presentation. The classification proposed by Frieden in 1986 is widely used.To establish whether, 34 years on, the Frieden classification still meets our needs.We conducted a retrospective chart review of all patients with a diagnosis of ACC presenting over a 25-year period to a tertiary paediatric dermatology department. We noted demographic data, clinical characteristics such as number, location and morphology of the lesions, imaging and genetic results where available and other associated abnormalities and grouped them according to Frieden's classification. For type 6 ACC (Bart syndrome) we reviewed neonatal photographs of all babies born with epidermolysis bullosa (EB) over 5 years.Excluding type 6, there were 56 children with ACC. The scalp was involved in 82.1% and type 1 was the commonest type. Over 5 years, 13 of 108 (12%) neonates with EB were born with the appearance of type 6 ACC. Two children did not fit Frieden's original classification and one had a previously undescribed association of ACC with cleft palate - ectodermal dysplasia syndrome.We conclude that Frieden's classification remains valid with some modifications. Type 3 ACC probably represents a mosaic RASopathy syndrome. Type 7 could cover non-genetic ACC attributable to trauma. Type 8 should be sub-divided into teratogenic and infective. Type 9 covers at least 4 subgroups. The classification will continue to evolve as new genes and pathomechanisms emerge.