Severe combined immunodeficiency disease (SCID) is an autosomal recessive disease occurring in Arabian horses. A recent discovery of a five base pair deletion in the gene encoding DNA-PK catalytic subunit has led to a PCR based test to screen for carriers of this disease. It has been suggested that the origin of this mutation arose from a stallion that originated in Poland. For this reason the occurrence of the SCID allele was tested on a representative sample of Polish horses. None of the 271 horses tested were carriers for this mutated allele.