There was no statistically significant difference in the frequency of severe neutropenia among the 3 genotypes of UGT1A1 (*1/*1, *1/*28 or *1/*6, and *28/*28, *6/*6, or *28/*6), although the frequency was numerically higher in the *28/*28, *6/*6, or *28/*6 genotype groups. This evidence concerns the gene UGT1A1 and neutropenia.