Genetic variants of the alphaS1 casein gene in goats determine the different casein and protein content of milk, variant milk processing quality and cheese flavour. The main seven alleles of alphaS1 casein belong to four groups: strong alleles, which code for a high alphaS1 content (3.6 g/L), medium alleles (1.6 g/L), weak alleles (0.6 g/L) and allele 0 (complete lack of alphaS1 casein). An original method was designed, based on PCR with three specific primers and mRNA isolated from milk somatic cells. The length of PCR products varied due to differences between alleles on cDNA level, since allele F has a 111 nt deletion of 9-11 exons, allele D is associated with deletion of 36 nt (exon 9), and allele E includes a 457 nt retropozon insertion in exon 19. Forty-nine goats coming from four different farms were genotyped. Each of the analysed goats is the carrier of at least one `strong' allele, which codes for the beneficial high level of alphaS1 casein.