Objective: To expand the spectrum of genetic causes of autosomal recessive cerebellar ataxia (ARCA). Case report: Two brothers are described who developed progressive cerebellar ataxia at 3 1/2 and 18 years, respectively. After ruling out known common genetic causes of ARCA, analysis of blood peroxisomal markers strongly suggested a peroxisomal biogenesis disorder. Sequencing of candidate PEX genes revealed a homozygous c.865_866insA mutation in the PEX2 gene leading to a frameshift 17 codons upstream of the stop codon. PEX gene mutations usually result in a severe neurological phenotype (Zellweger spectrum disorders). Conclusions: Genetic screening of PEX2 and other PEX genes involved in peroxisomal biogenesis is warranted in children and adults with ARCA