In neutrophils of a chronic granulomatous disease (CGD) patient with a lack of p67phox the mRNA for p67phox was present in normal amount and size. This mRNA was reverse transcribed, and the coding region was analyzed by single-strand conformation polymorphism analysis. Direct DNA sequencing allowed the identification of a A479-to-T and A481-to-G substitution in exon 5 of the p67phox gene resulting in a double nonconservative amino acid change 160Lys-to-Glu and 161Asp-to-Val (D160V-K161E). This defect was found in the genomic DNA of this patient in heterozygous state and does not correspond to those previously found in other cases of CGD lacking the p67phox.