Keloid disease (KD) is a common fibroproliferative disorder of unknown aetiopathogenesis, with highly unsatisfactory treatment. Therefore, it is crucial to have a robust and clinically relevant model for studying KD pathobiology as well as preclinical testing of potential KD therapeutics. However, the unique occurrence of KD in human skin and the corresponding lack of animal models pose a major challenge in KD research. Therefore, we developed a simplified assay for the serum-free, long-term organ culture of KD tissue that facilitates quantitative analyses of major KD read-out parameters. Four millimetre KD punches embedded in a collagen matrix and organ-cultured at the epidermis air-liquid interphase (ALI) in supplemented William's E medium showed optimal tissue, cell and RNA preservation for up to 6 weeks (as measured by H & E and Pyronin Y histochemistry as well as by MTT assay, lactate dehydrogenase release and quantitative Ki67/TUNEL immunohistomorphometry). The keloid phenotype persisted well during this period, as shown by collagen-I and -III synthesis (Herovici's histochemistry staining and ELISA), and analysis of the expression of significant KD markers (CD3, CD20, CD31, CD34, CD56, tryptase, Langerin, vimentin, neutrophil elastase, CTGF and Collagen). To functionally evaluate whether this assay can test the response to candidate therapeutics, dexamethasone, a glucocorticosteroid often used in KD therapy, was administered. Indeed, dexamethasone significantly reduced the keloid volume and cellularity plus induced epidermal shrinkage. Therefore, this novel assay provides a quantitative, clinically relevant model system for studying KD pathobiology and response to treatment.