Severe combined immunodeficiency disease (SCID) of horses is an autosomal, recessive hereditary disease occurring among Arabian or crossbred Arabian horses. The genetic defect responsible was previously identified as a 5-base pair deletion in the gene encoding the catalytic subunit of the DNA dependant protein kinase (DNA-PKcs). This study was carried out to determine the frequency of SCID and identify horses carrying the gene for SCID among Arabian and Arabian crossbred stallions and mares in Morocco using a DNA-based test. Twenty-one horses were SCID carriers: 14 (7%) Arabians, 6 (4%) Arab-Barbs and one (33%) Anglo-Arab. After analysing their genealogy, 3 imported stallions were identified that disseminated the mutant gene of DNA-PKcs in Morocco.