Objective severity scores facilitate clinical care and research. However, the rarity and heterogeneity of epidermolysis bullosa (EB) make scoring difficult. To develop a severity score covering all subtypes of EB at all ages that is simple, valid, sensitive and reliable. Score items and weightings were generated by expert consensus, and refined for content and face validity. The Birmingham EB Severity (BEBS) score was tested on 97 patients aged 0-64 years. Eleven items were scored: area of damaged skin, involvement of nails, mouth, eyes, larynx and oesophagus, scarring of hands, skin cancer, chronic wounds, alopecia and nutritional compromise. Area was allocated 50 points, and the 10 other items 5 points each, giving a maximum score of 100. Lowest BEBS scores occurred in Weber-Cockayne EB simplex (median 1.0; range 0.1-3.0; n = 12), highest scores in generalized non-Herlitz junctional EB (28.5; 5.0-62.0; n = 7), Hallopeau-Siemens recessive dystrophic EB (HS-RDEB) (22.9; 4.3-69.0; n = 23) and Herlitz junctional EB (H-JEB) (14.4; 2.5-49.3; n = 9), and intermediate scores in dominant dystrophic EB (5.3; 0.5-15.9; n = 19), Dowling-Meara EB simplex (DM-EBS) (6.3; 2.8-22.5; n = 16) and non-Hallopeau-Siemens recessive dystrophic EB (7.8, 2.8-27.8; n = 11). Intra- and interobserver correlations were high. With age, scores increased for H-JEB (r = 0.9, P = 0.001) and HS-RDEB (r = 0.73, P = 0.001) and decreased for DM-EBS (r = -0.62, P = 0.01), with positive but nonsignificant correlations for the other types. The BEBS score appears valid and reproducible, gives appropriate scores for different subtypes, and reflects changes with age.