To define the target of chromosome 17p deletions, allelic losses in the 17p11.2 to 13.3 regions of 32 ovarian cancers were investigated. Twenty-one (68%) of 31 informative cancers had deletions on chromosome 17p. None of these 21 cancers involved deletions in the entire chromosome 17p even if deletions of a small chromosome region were infrequent. Of these 21, 17 cancers contained deletions at 17p13.1 or neighboring regions. The remaining 4 cancers with 17p deletions were uninformative for deletions at 17p13.1. Thus, most 17p deletions seemed to target the 17p13.1 region in ovarian cancers. Of the 30 ovarian cancers screened, 6 contained p53 mutations. One p53 allele was lost as a consequence of deletion and the other was mutated in 4 cancers. Seventeen cancers with deletions on 17p showed no evidence of p53 mutations. Thus, deletions on 17p that are common in ovarian cancers are not always accompanied by p53 gene mutations.