Abstract: Nineteen open reading frames (ORFs) in the left arm of chromosome XI of the yeast Saccharomyces cerevisiae were inactivated. This was done by producing single-gene or contiguous-gene deletions in haploid and diploid strains. Four deletions are lethal to the corresponding haploid strains, and two result in a failure to grow on a rich glycerol medium. Complementation experiments showed that five of the six identified phenotypes were due to deletion of a single gene (ORFs YKL173w, YKL172w, YKL165c, YKL154w are essential, and YKL160w is required for growth on glycerol medium). One of the phenotypes observed on glycerol medium was not suppressed by the corresponding deleted genes. None of the other deletions, covering 13 ORFs in all, gave rise to any obvious phenotype when the cells were grown at three different temperatures on rich glycerol or glucose medium or on minimal synthetic medium.