Gene conversion events are often overlooked in analyses of genome evolution. In a conversion event, an interval of DNA sequence (not necessarily containing a gene) overwrites a highly similar sequence. The event creates relationships among genomic intervals that can confound attempts to identify orthologs and to transfer functional annotation between genomes. Here we examine 1,616,329 paralogous pairs of mouse genomic intervals, and detect conversion events in about 7.5% of them. Properties of the putative gene conversions are analyzed, such as the lengths of the paralogous pairs and the spacing between their sources and targets. Our approach is illustrated using conversion events in primate CCL gene clusters. Source code for our program is included in the 3SEQ_2D package, which is freely available at www.bx.psu.edu/miller_lab/ .