In a screen for DNA repair-defective mutants in the fungus Ustilago maydis, a gene encoding a BRCA2 family member, designated here as Brh2, was identified. A brh2 null allele was found to be defective in allelic recombination, meiosis, and repair of gaps and ionizing radiation damage to the same extent as rad51. Frequent marker loss in meiosis and diploid formation suggested that genomic instability was associated with brh2. This notion was confirmed by molecular karyotype analysis, which revealed gross chromosomal alterations associated with brh2. Yeast two-hybrid analysis indicated interaction between Brh2 and Rad51. Recapitulation in U. maydis of defects in DNA repair and genome stability associated with brh2 means that the BRCA2 gene family is more widespread than previously thought.