Abstract: In the frame of the European Network for Functional Analysis (EUROFAN), two regions from chromosome XI covering 54kb have been subjected to 'mass-murder'. Ten deletions covering 23 novel open reading frames (ORFs) were constructed in haploid and diploid strains. Six deletions were lethal in haploid strains. One deletion caused slow germination of spores and slow cellular growth, and another one was associated with both cellular growth thermosensitivity and poor growth on glycerol. These two defects were assigned to two different genes. All mutant phenotypes were complemented by a single gene, enabling us to identify five genes essential for vegetative growth, three genes with detectable phenotype and 15 dispensable genes under standard physiological conditions.