In the context of the EUROFAN project, we have carried out the systematic disruption of seven ORFs on chromosome IV of Saccharomyces cerevisiae using the long flanking homology technique to replace each ORF with the KanMX cassette. Targeted disruption of YDL057w, YDL012c, or YDL010w with YDL009c (the two ORFs overlap) confers no overt defects in haploid growth on a variety of media at different temperatures, in mating, or in the sporulation of diploids homozygous for the disruption. By contrast, YDL008w and YDL003w disruptants are non-viable. The product of YDL008w (elsewhere identified as APC11) is a component of the anaphase promoting complex. YDL003w (also termed MCD1) is a homologue of Schizosaccharomyces pombe rad21, an essential gene implicated in DNA double-strand break repair and nuclear organization in fission yeast. In budding yeast, this ORF has been shown by several laboratories to encode a protein involved in sister chromatid cohesion and chromosome condensation. The remaining ORF, YDL005c (also termed MED2), encodes a component of the transcriptional activator complex known as Mediator. Disruption of YDL005c confers a modest slow growth phenotype on rich medium and a more severe phenotype on minimal medium, aberrant cellular morphology, and mating defects; diploids homozygous for the disruption cannot sporulate.