Eleven chromosomal deficiencies and several rearrangements in the Pu-tud region of chromosome 2R have been generated and examined cytologically. The Pu locus has been localized to chromosome bands 57C5-6 and tud to 57C7-8. Mutagenesis within the region defined by the deletion intervals has resulted in the isolation of 92 new lethal mutations. Seventy-six of these mutations have been separated into 16 complementation groups that have been ordered and placed cytologically by deletion mapping. All new alleles fully complement tud for both lethal and grandchildless phenotypes. The largest number of new mutations, a total of 25, are Pu alleles.