Experimental noise and noncontiguous clone inserts can pose serious problems in reconstructing genomic maps from hybridization data. We describe an algorithm that easily identifies false positive signals and clones containing chimeric inserts/internal deletions. The algorithm "dechimerizes" clones, splitting them into independent contiguous components and cleaning the initial library into a more consistent data set for further ordering. The effectiveness of the algorithm is demonstrated on both simulated data and the real YAC map of the whole genome of the fission yeast Schizosaccharomyces pombe.