A T-deletion at position 10 of exon 4 for catalase gene was reported as a novel mutation, causing a new genetic type of acatalasemia in Japan. This mutation, destroying a Hinf1 recognition site, was searched for in Hungarian acatalasemic (2) and hypocatalasemic (22) patients and in controls (27) by Hinf1 digestion and sequence analyses of a 203 bp polymerase chain reaction (PCR) product containing the entire exon 4. The Hinf1 polymorphism did not reveal any difference between controls and hypocatalasemic as well as acatalasemic patients. These results were confirmed by sequence analyses showing the T nucleotide for the two acatalasemic and for one unrelated hypocatalasemic patient, as well as for two controls. These findings represent further evidence that acatalasemia is heterogeneous at the DNA level.