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Reproductive tracts were collected from 87 female black bears (Ursus americanus) killed by hunters in northeastern and north-central Pennsylvania during November 1974 and 1975. Pregnant animals carried an average of 2.75 corpora lutea. Corpora lutea were significantly larger in tracts that had implantations than in tracts during the delay stage. The sources of ova were found to be equally divided between ovaries. Twelve blastocysts and 22 implanted embroys were examined. Variation in development stage among these samples indicated that implantation occurred late in November or early in December. An average of 2.88 placental scars were observed in animals bearing scars. Potential recruitment from first breeding (2.39 animals) was significantly less than from second or later breedings (3.23 animals). Minimum breeding age for female bears was 2.5 years, at which time 38 percent of the animals bred. The majority of females bred by the time they were 3.5 years old. A very low incidence of nonbreeding females was found.