Spinobulbar muscular atrophy (SBMA) is an X-linked form of motor neuron disease characterized by progressive atrophy of the muscles, dysphagia, dysarthria and mild androgen insensitivity. SBMA is caused by CAG repeat expansion in the androgen receptor gene. CAG repeat polymorphism was analysed in a Polish control group (n = 150) and patients suspected of SBMA (n = 60). Normal and abnormal ranges of CAG repeats were established in the control group and in 21 patients whose clinical diagnosis of SBMA was molecularly confirmed. The ranges are similar to those reported for other populations.