Previous allelotyping studies of epithelial ovarian carcinoma suggest that loss of heterozygosity on chromosome 14q may be a common genetic alteration in this tumor type. The purpose of this study was to determine a precise frequency of chromosome 14q allelic loss in ovarian carcinomas and to define a minimal region(s) of deletion. Seventy-six ovarian carcinomas representative of the complete spectrum of grade, stage, and histological subtype were selected for PCR-based deletion mapping analysis using 15 highly polymorphic microsatellite markers spanning the length of this chromosome arm. Loss of heterozygosity was observed in 49% of the tumors studied, placing 14q among the most frequently affected chromosomal regions in ovarian cancer. Deletions were observed in all tumor grades and stages and in all histological subtypes except tumors of low malignant potential. Deletion of the entire chromosome arm was rare; the majority of tumors displayed partial losses, providing an informative basis for detailed deletion mapping. Two distinct minimal regions of deletion were delineated. One region was defined by markers D14S80 and D14S75 at 14q12-13, and the other region was defined by markers D14S65 and D14S267 at 14q32. These data implicate the involvement of two tumor suppressor genes on chromosome 14q in a substantial fraction of ovarian carcinomas.