Abstract
In connection with the fact that BB rats are homogeneous for haplotype RTlu and their parental Wistar rat stock is heterogenous for haplotypes RTlu and RTla the influence of the RTl haplotypes on some hematologic and metabolic traits was studied. The findings indicate marked differences between BB rats and their parental strain independent of haplotype RTl so that the changed genetic background of the BB rat rather than the haplotype per se seems to be the reason for the differences observed.