B cell Ag receptor editing is a process that can change κ antigen recognition specificity of a B cell receptor through secondary gene rearrangements on the same allele. In this study we used a model mouse pre-B cell line (38B9) to examine factors that might affect allelic targeting of secondary rearrangements of the κ locus. We isolated clones that showed both productive and nonproductive rearrangements of one κ allele, while retaining the other κ allele in the germline configuration (κ+/κ°or κ-/κ°). In the absence of any selective pressures, subsequent rearrangement of the germline alleles occurred at the same frequency as secondary rearrangement of the productive or nonproductive rearranged alleles. Because 38B9 cells lack Ig heavy chains, we stably expressed μ heavy chain protein in 38B9 cells to determine whether heavy-light pairing might affect allelic targeting of secondary κ rearrangements. Although the expression of heavy chain was found to both pair with and stabilize κ protein in these cells, it had no effect on preferential targeting Vκ-Jκ receptor editing compared with rearrangement of a germline allele. These studies suggest that in the absence of selection to eliminate autoreactive Vκ-Jκ genes, there is no allelic preference for secondary rearrangement events in 38B9 cells.