We describe a simple method for the construction of large chromosomal deletions in yeast. Diploid yeast cells were transformed with DNA fragments that replace large regions of the chromosomes by homologous recombination. Using this method, we have constructed a telocentric chromosome III in which approximately equal to 100 kilobases (kb) of DNA has been removed from the left arm of the chromosome, so that the centromere is 12 kb from the left telomere. This telocentric chromosome is mitotically stable. Its rate of loss in a diploid strain is 2.5-7.4 X 10(-4) per cell division compared to a rate of loss of 0.36-1.8 X 10(-4) per cell division for a normal chromosome III. It also segregates 2+:2- with fidelity during meiosis. The construction of systematic deletions in a chromosome should be useful in determining the essential features for proper chromosomal segregation and replication.